June 20102 Red blood cells (erythrocytes) transport oxygen from
the alveolar surface in the lungs to the respiring tissues. A group
of nine athletes (A to I) wanted to see if training for two weeks
at a mountain camp, 2000 m above sea level, had an effect on the
number of red blood cells in their blood. Samples of blood were
taken from each of the athletes at their normal training camp at
sea level. Blood samples were taken again after two weeks of
training at the mountain camp. A copy of the raw data collected is
given below: Number of red blood cells x1012 per dm3 blood before
mountain training A 5.0B 5.1C 4.9D 5.3E 5.4 F 5.0 G 4.8 H 5.1I 5.5
Number of red blood cells x1012 per dm3 blood after mountain
training A 4.9 B 5.3 C 5.7 D 5.5 E 5.6 F 5.4 G 5.3 H 5.6 I 5.1 (a)
Write a null hypothesis for this
investigation.(1)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................(b)
Calculate the difference in the number of red blood cells before
and after the mountain training for each athlete. Prepare a table
to display the raw data and your calculated values.(4)
(c) Identify an anomalous result in the data from the
athletes.(2)..........................................................................................................................................................
Give one reason for your
answer...............................................................................................................................................................................................................................................................................................................................................................................................................................................................................(d)
Calculate the mean number of red blood cells per dm3 of blood for
the group of athletes before and after mountain training.(2)
Mean number of red blood cells before training
............................................... Mean number of red
blood cells after two weeks training at 2000 m
..........................................(e) Present the
calculated mean red blood cell counts in a suitable graphical form.
(3)
(f) A t-test was applied to the data to test the null
hypothesis. The calculated value of t was 2.24. The table below
shows the critical values of t with 16 degrees of freedom, at
different significance levels.
What conclusion can be drawn from this investigation? Use the
information in the table to explain your answer.
(3)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 15 marks)
January 20112 Rennin is an enzyme, found in the stomach of
mammals, that can form solid clots in milk. Rennin is often used in
the first stage of cheese production. A student was interested in
discovering which conditions would be ideal for making cheese. She
wanted to determine which concentration of rennin was likely to
give her suitable rates of clotting of milk. She prepared the
following test tubes: Fourteen test tubes with 5 cm3 milk Twelve
test tubes, each containing 5 cm3 of different concentrations of
rennin Two test tubes with 5 cm3 distilled water She placed these
test tubes in a water bath at 30C and left them for 10 minutes. The
content of each test tube containing milk was added to a test tube
containing either rennin or distilled water. These were mixed and
returned to the water bath. The time taken for the milk to clot
(thicken) was recorded. A copy of the students raw results are
below.
(a) Explain why the test tubes containing milk, rennin and
distilled water were left in the water bath for 10 minutes before
they were
mixed.(1)..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(b) Convert the times recorded into the SI units of seconds and
prepare a suitable table to display these raw results and each of
the following.(i) The mean time for clotting for each concentration
of rennin. (ii) The mean rate of milk clotting, calculated using
the equation below
(5)
(c) Show the effect of changing the rennin concentration on the
mean rate of milk clotting, in a suitable graphical form.(3)
(d) Identify an anomalous result in the data for the different
rennin concentrations.
(2)..........................................................................................................................................................
Give one reason for your
answer.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(e) The student applied a Spearman rank correlation to explore the
relationship between the rate of clotting and the rennin
concentration. From her calculation, she obtained a Spearman rank
correlation of 1.0. Table of significance levels for Spearman rank
correlation. What conclusion can be drawn from this investigation?
Use the information in the table to explain your answer.
(2)..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(f) Give an explanation for the relationship between rennin
concentration and the rate of clotting of
milk.(2)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 15 marks)
May 20112 A student decided to investigate whether eating
breakfast every day had an effect on the body mass of students in
her class.She selected twelve students (A to L), measured their
body mass and asked if they ate breakfast regularly.A copy of her
raw results is shown below.
(a) Write a suitable null hypothesis for this
investigation.(1)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................(b)
Prepare a suitable table to display the data obtained and calculate
the mean body mass for students who regularly eat breakfast and
those who do not.(4)
(c) Using a suitable graphical form, compare the effects of
eating breakfast regularly or not on the body mass of these
students. (3)
(d) The student applied a t-test to the data she obtained. She
obtained a result of t = 3.09 from her calculation. The table below
shows critical values of t with 10 degrees of freedom, at different
significance levels.
What conclusions can be drawn from this investigation? Use the
information provided in the table above and in the graph you have
drawn.(3)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(e) Suggest why it may not be reasonable to draw a firm
conclusion from the results of this
investigation.(3)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 14 marks)
January 20122 A student investigated the effect of caffeine
concentration on the heart rate of animals.He selected five Daphnia
(A to E), and measured the heart rate, in beats per minute, of each
of them in water. This was repeated using six concentrations of
caffeine solution (0.01%, 0.1%, 0.5%, 1.0%, 2.0%, 5.0%).A copy of
his raw results (starting from water (0%) on the left increasing to
5% caffeine solution on the right) for each Daphnia is shown
below.A 176, 240, 256, 260, 268, 274, 282.B 178, 238, 256, 262,
270, 282, 274.C 184, 244, 260, 264, 270, 278, 284.D 172, 236, 248,
254, 260, 270, 278.E 182, 246, 264, 266, 268, 272, 286.(a) Write a
suitable null hypothesis for this
investigation.(1)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................(b)
State and explain one ethical reason why the student chose to use
Daphnia for this
investigation.(2)............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(c)
Calculate the mean heart rates for each concentration of
caffeine.(3)
Mean heart rate at 0.0% caffeine concentration
......................................................................
Mean heart rate at 0.01% caffeine concentration
......................................................................
Mean heart rate at 0.1% caffeine concentration
......................................................................
Mean heart rate at 0.5% caffeine concentration
......................................................................
Mean heart rate at 1.0% caffeine concentration
......................................................................
Mean heart rate at 2.0% caffeine concentration
......................................................................
Mean heart rate at 5.0% caffeine concentration
.......................................................................(d)
Prepare a table to display the raw data and your calculated values
for the mean heart rates.(3)
(e) On the graph paper below, draw a suitable graph to
illustrate the effect of caffeine concentration on the mean heart
rate of Daphnia. (3)(f) The student used a statistical test to
investigate the significance of the correlation between the mean
heart rates and the caffeine concentrations. His calculation gave a
correlation value of 1.00. The table below shows significance
levels and correlation values for this statistical test.
What conclusions can be drawn from this investigation? Use the
information provided in the table above and in the graph you have
drawn, together with your knowledge and understanding, to explain
your answer.
(4)..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 16 marks)
May 20122 A student decided to investigate habituation in Giant
African Land snails (Achatina fulica).
The student selected a snail (A) and placed it on a glass plate
across which it was able to move. The student tapped the plate with
a glass rod, next to the snail, causing the snail to stop moving
and withdraw into its shell. The student recorded the time, in
seconds, it took for the snail to re-emerge from its shell and
start moving again. The student tapped the plate at the start of
the investigation and then every two minutes for a total of 12
minutes. The investigation was repeated with two other snails (B
and C). A copy of the raw results for each snail is shown below.A
90, 40, 30, 10, 0, 0, 2B 108, 60, 40, 15, 5, 0, 0C 80, 48, 80, 20,
0, 0, 0 (a) Write a suitable null hypothesis for this
investigation.(1)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(b) Calculate suitable means from the raw results and prepare a
table to display these and the raw data for this
investigation.(4)
(c) On the graph paper below, draw a suitable graph to show the
effect of repeated tapping on the time taken for a snail to start
moving again.(3)
(d) State an anomalous result in the
data.(2)..........................................................................................................................................................
Give one reason for your
answer.....................................................................................................................................................................................................................................................................................................................(e)
The student used a statistical test to investigate the significance
of the correlation between the mean time for the snails to start
moving and the repeated tapping. His calculation gave a negative
correlation value of 0.93. The table below shows significance
levels and correlation values for this statistical test.
What conclusions can be drawn from this investigation? Use the
information provided in the table above and on the graph you have
drawn, together with your knowledge and understanding of
habituation, to explain your
answer.(5)..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 15 marks)
January 20132 A student decided to investigate the effect of
listening to music on short-term memory. She recorded how many
numbers were correctly recalled from a grid containing 25 random
numbers. She tested 15 members of her class (students A to O) with
no music. She repeated the test three times for each student and
calculated the mean for each student. She repeated the tests with
the same 15 students, while they listened to some loud music. A
copy of her mean results for each student is shown below:
(a) Write a suitable null hypothesis for this
investigation.(1)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................(b)
Prepare a suitable table to display the data obtained and calculate
the overall mean for the numbers recalled by these 15 students,
both with music and with no music.(4)
(c) On the graph paper below, draw a suitable graph to show the
effect of listening to music on the overall mean for the numbers
recalled by these students. Include on your graph an indication of
the variability in the overall means.(3)
(d) The student applied a t-test to explore the significance of
her results. She obtained a result of t = 3.30 from her
calculation. The table below shows some critical values for t-test
calculations.
What conclusion can be drawn from this investigation? Use the
information provided in the table and in the graph you have drawn,
together with your knowledge and understanding to explain your
answer.(5)............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(e) Suggest why it may not be reasonable to draw a valid
conclusion from the results of this
investigation.(3)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 16 marks)
May 20132 Earthworms are animals that improve the quality of
soil needed for plant growth.Farmers often plough the soil before
planting crops in a field. A farmer wanted to investigate the
effect of ploughing on the presence of earthworms. He used
different methods to plough two fields (field A and field B), next
to each other. These fields were then left for one month. The
farmer then randomly placed quadrats (0.5 m 0.5 m) in field A. In
each quadrat he poured a weak detergent solution onto the soil. He
then counted the number of earthworms that came to the surface in
each quadrat. He repeated this process in field B. A copy of the
farmers raw results is shown below: Field A: 10, 4, 13, 9, 9, 3, 8,
5, 4 Field B: 15, 6, 12, 0, 3, 8, 9, 10, 7, 4, 6 (a) Write a
suitable null hypothesis for this
investigation.(2)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(b) Prepare a suitable table to rank the data obtained. Identify
the median number of earthworms from the quadrats in each
field.(4)
(c) On the graph paper below, draw a suitable graph to show the
effect of different methods of ploughing on the median number of
earthworms from the quadrats in each field. Include on your graph
an indication of the variability in the data.(3)
(d) The farmer decides to apply the Mann-Whitney U test to the
data. This statistical test determines if the difference between
the medians is significant. The calculations produced two U values
for this set of data. In order to support a difference between the
two medians, the smaller U value must be the same as, or less than,
the critical value. He obtained a result of U = 50 from the
calculation (the smaller value). The table below shows the critical
values for the Mann-Whitney U test at the p = 0.05 level.
What conclusions can be drawn from this investigation? Use the
information provided in the table above and in the graph you have
drawn.(4)..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(e)
Suggest why it may not be reasonable to draw a valid conclusion
from the results of this
investigation.(3)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 16 marks)
January 20142 A student decided to investigate whether drinking
coffee containing caffeine had an effect on reaction times.She
selected 27 students who regularly had drinks containing
caffeine.The students did not have any drinks containing caffeine
for 24 hours before the investigation. On the morning of the
investigation, the students drank either one cup of coffee
containing caffeine or one cup of coffee with no caffeine.The
students then went to their first lesson. Immediately after the
lesson, the reaction times of the students were measured in
milliseconds (ms).The raw results are shown below.Group given
coffee containing caffeine355 ms, 310 ms, 270 ms, 450 ms, 350 ms,
316 ms, 298 ms, 368 ms, 394 ms,347 ms, 246 ms, 340 ms, 415 ms, 274
ms, 300 msGroup given coffee with no caffeine426 ms, 440 ms, 510
ms, 412 ms, 398 ms, 450 ms, 340 ms, 484 ms, 365 ms,410 ms, 380 ms,
264 ms(a) Write a suitable null hypothesis for this
investigation.(2)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(b) Calculate the mean value for each group.Prepare a suitable
table to display the mean value and the sample size for each
group.(3)
(c) On the graph paper below, draw a suitable graph to show the
effect of caffeine on mean reaction times and the variability of
the data.(3)
(d) The student applied a t-test to the data she obtained. She
obtained a valueof t = 3.03 from her calculation.The table below
shows critical values of t with different degrees of freedom at
different significance levels.The number of degrees of freedom is
calculated using the formula shown below.Degrees of freedom = (n1
1) + (n2 1)where n1 and n2 represent the size of the groups being
compared.
What conclusions can be drawn from this investigation?Use the
information provided in the table above and in the graph you have
drawn to explain your
answer.(3)......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(e) Suggest why it is difficult to draw a valid conclusion from the
results of this
investigation.(3)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 14 marks)
June 20142 Forced expiratory volume (FEV1), is the maximum
volume of air that can be forcibly expired from a persons lungs in
one second.Nigel decided to investigate whether the height of a
person is related to FEV1.He selected 8 students of different
heights. For each student he measured the FEV1 three times. The
results of this investigation are shown below.
(a)Write a suitable null hypothesis for this investigation.
(2)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(b) Calculate the mean FEV1 for each student. Display the data for
the height and the mean FEV1 for each student in a suitable table.
(3)
(c) On the graph paper below draw a suitable graph to show the
relationship between height and mean FEV1.Include on your graph an
indication of the variability in the data. (3)
(d) Nigel used a statistical test to investigate the
significance of the relationship between the height of an
individual and FEV1. His calculation gave a value of 0.65.The table
below shows values for this statistical test at three significance
levels of 0.1, 0.005 and 0.01.
Use the information provided in this table and in your graph to
draw conclusions from this
investigation.(4)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(e) Suggest why it may not be reasonable to draw a valid conclusion
from the results of this investigation.
(3)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 15 marks)
January 20152 Ultraviolet (UV) light can be used to kill
microorganisms. A student decided to investigate the effect of UV
light on the survival of bacteria. The student spread bacteria on
three agar plates. Each plate was then exposed to UV light for one
minute. She placed the agar plates in an incubator. After 48 hours,
she recorded the number of bacterial colonies on each plate. The
procedure was repeated for exposure times of 2, 3, 4 and 5 minutes.
A copy of her raw results is shown below. 1 minute exposure to UV
light: 302, 282 and 322 colonies 2 minutes exposure to UV light:
187, 215 and 231 colonies 3 minutes exposure to UV light: 174, 108
and 129 colonies 4 minutes exposure to UV light: 70, 94 and 82
colonies 5 minutes exposure to UV light: 37, 47 and 21 colonies (a)
Write a suitable null hypothesis for this investigation. (2)
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
(b) Calculate the mean number of bacterial colonies for each UV
exposure time. (2)
Mean number of bacterial colonies after 1 minute UV exposure
............................ Mean number of bacterial colonies
after 2 minutes UV exposure .......................... Mean number
of bacterial colonies after 3 minutes UV exposure
.......................... Mean number of bacterial colonies after
4 minutes UV exposure .......................... Mean number of
bacterial colonies after 5 minutes UV exposure
.......................... (c) Prepare a suitable table showing the
raw data and your calculated values for the mean number of
bacterial colonies. (2) (d) On the graph paper below, draw a
suitable graph to show the effect of UV light on the survival of
bacteria. Include on your graph an indication of the variability of
this data.(3)
(e) The student used a statistical test to investigate the
significance of the correlation between the exposure time to UV
light and the number of bacterial colonies. A negative correlation
with a value of 0.99 was found. The table below shows the critical
values for a significance level of p = 0.05 when using this
statistical test. Number of meansCritical values for a significance
level of p = 0.05
4 1.00
5 0.90
6 0.83
7 0.71
8 0.64
9 0.60
What conclusion can be drawn from the results of this
investigation? Use the information given and the graph you have
drawn to explain your answer. (4)
..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(f ) Suggest why it may not be reasonable to draw valid conclusions
from the results of this investigation. (3)
..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(Total for Question 2 = 16 marks)