Transcript
RESEARCH MEDTHODOLOG
Y
GROUP MEMBERS
Sanaullah MallahShazia MallahSaba Pervez
Muhammad AliZainab Younis
Muhibullah Nahrio
TOPIC
VALIDITY AND RELIABLITY
OBJECTIVES• What is validity and reliability
• How and why we use them as tools
• Methods , types, Factors
• Its importance and both concepts together
AN OVERVIEW OF PRESENTATION AS A WHOLE
AND RELIABILITYby
SHAZIA MALLAH
ITS TYPES AND METHODES AS A TOOLS TO KNOW HOW WE USE
IT AND FACTORS
Major types of validityContent-related evidence of validity
Criterion-related evidence of validity
Construct-related evidence of validity
1
2
3
FACTORS AFFECTING VALIDITY
Major Methods of Reliability TEST-RETEST METHOD
EQUIVALENT-FORMS METHOD
INTERNAL-CONSISTENCY METHODS
1
2
3
FACTORS AFFECTING RELIABILITY
VALIDITY AND RELAIBLITY IMPORTANCE AND VALIDITY AND RELIABILTY TOGETHER
EXAMPLEif your scale is off by 5 pounds, it reads your
weight every day with an excess of 5pounds. The scale consistently reports the same weight every day, but it adds 5pounds to your true weight.
•
EXAMPLE• if your scale is off by 5 lbs, it reads your
weight every day with an excess of 5lbs. The scale is reliable because it consistently reports the same weight every day, but it is not valid because it adds 5lbs to your true weight. It is not a valid measure of your weight.
•
• The consistency of the scores obtained—how consistent they are.
• the consistency of your measurement instrument
• the degree to which an instrument measures the same way each time it is used under the same condition with the same subjects
RELAIBLITY
What do I mean by…?
© A. Taylor Do not duplicate without author’s permission
16
• Reliability alone does not mean that you have a good instrument however.
• Imagine the following reliable instrument:
0165Every morning GALTON gets on the scale and every morning it reads 165 lbs.
It seems pretty reliable since GALTON hasn’t gained or lost any weight.
One day an elephant got on GALTYON’s scale and it still read 165 lbs.!How is this scale reliable?It does measure the same way under the same conditions (GALTON’s) – but a lot of other conditions too (the elephant and who knows what else).
RELIABILITY
© A. Taylor Do not duplicate without author’s permission
17
What in the world is a measurement instrument?• Any tool that you use to measure with…
• What “instrument” might you use to measure the following items?
1. How heavy the apples are
2. How hot the meat is
3. How much orange juice there is
4. How tall the wall is
a scale
a meat thermometer
a measuring cup
a yardstick
© A. Taylor Do not duplicate without author’s permission
18
Can it measure how loud the radio is? how full the
glass is?
how smart the girl is?
The ruler may be reliable (and perhaps even valid) but not in these situations!It is only valid for measuring length.
Reliable but not Valid
19
What would the following instruments measure?
The size of someone’s foot
EyesightThe perfect amount of spaghetti!
More on Instruments
© A. Taylor Do not duplicate without author’s permission
20
What instrument you choose depends on
several factors• Ease of use – do you know how to use it?
.
• Access – do you have access to the instrument?
• Appropriateness – is it the best tool for what you are measuring?
• Accuracy – how precise do your measurements have to be?
• Cost – how expensive is it to use the instrument or interpret the results?
.
SANAULLAH MALLAH
• Validity refers to how well a test measures what it is purported to measure.
• appropriateness, correctness, meaningfulness, and usefulness of the specific inferences researchers make based on the data they collect.
VALIDITY
© A. Taylor Do not duplicate without author’s permission
23
Validity asks if an instrument measures what it is supposed to
how “true” or accurate the measurement is.
What
is
Validity?
EXAMPLE
EXAMPLE
SABA PERVEZ
VALIDITY TYPES AS A TOOLAND ITS FACTORS
Major types of validityContent-related evidence of validity
Criterion-related evidence of validity
Construct-related evidence of validity
1
2
3
Major types of validityContent-related evidence of validity1
the content and format of the instrument. How appropriate is the content? How comprehensive? Does it logically get at the intended variable? How adequately does the sample of items or questions
represent the content to be assessed? Is the format appropriate?
Major types of validity Criterion-related evidence of validity 2
the relationship between scores obtained using the instrument and scores obtained using one or more other instruments or
measures
Major types of validityConstruct-related evidence of validity3
The nature of the psychological construct or characteristic being measured by the instrument. How well does a measure of the construct explain differences in the behavior of individuals or their
performance on certain tasks.
FACTORS AFFECTING VALIDITY
1. Test-related factors2. The criterion to which you compare
your instrument may not be well enough established
3. Intervening events4. Reliability
MUHIBULLAH
RELIABILITY METHOEDS AS A TOOL
AND ITS FACTORS
Major Methods of Reliability TEST-RETEST METHOD
EQUIVALENT-FORMS METHOD
INTERNAL-CONSISTENCY METHODS
1
2
3
Major Methods of ReliabilityTEST-RETEST METHOD1
The test-retest method involves administering the same test twice to the same group after a certain
time interval has elapsed
Major Methods of ReliabilityEQUIVALENT-FORMS METHOD2
When the equivalent-forms method is used, two different but equivalent (also called alternate or parallel ) forms of an instrument are administered to the same group of individuals during the same
time period
Major Methods of ReliabilityINTERNAL-CONSISTENCY METHODS3
Internal consistency reliability is a measure of how well the items on the test measure the same
construct or idea.
FACTORS AFFECTING RELIABILITY
1. Test length2. Test-retest interval3. Variability of scores4. Guessing5. Variation within the test situation
ZAINAB YOUNIS
VALIDITY AND RELAIBLITY IMPORTANCE
IMPORTANCE
Reliability and validity are important concepts in research. The everyday use of these terms
provides a sense of what they mean (For example, your friends are reliable. Your
opinion is valid). In research, their use is a little more complex
IMPORTANCERELIABILITY
TEST-RETEST METHOD
EQUIVALENT-FORMS METHOD
INTERNAL-CONSISTENCY METHODS
VALIDITY Content-related
evidence of validity
Criterion-related evidence of validity
Construct-related evidence of validity
IMPORTANCE
ERRORS OF MEASUREMENT
VALIDITY AND RELIABILTY TOGETHER
Putting Reliability and Validity
TogetherEvery instrument can be evaluated on two dimensions:ReliabilityHow consistent it is given the same conditions
ValidityIf it measures what it is supposed to and how accurate it is
Putting Reliability and
Validity Together
Imagine that I have 3 fish tank thermometers, a blue one, a red one, and a green one.
The blue one always reads the same temperature no matter how hot or cold the water is.
The red one shows a different temperature every time even if I just measured it 5 seconds earlier.
The green one seems to read accurately, warm when the water is warm and cold when the water is cool.
© A. Taylor Do not duplicate without author’s permission
48
Is it consistent?Is it measuring what it
is supposed to? Is it reliable? Is it valid?
Blue always reads the same temperature no matter what
Red different temperature every time even if nothing has changed
Green warm when the water is warm and cold when the water is cool
Complete the chart below
49
Is it consistent?Is it measuring what it
is supposed to? Is it reliable? Is it valid?
Blue always reads the same temperature no matter what
Red different temperature every time even if nothing has changed
Green warm when the water is warm and cold when the water is cool
Yes
No
Yes, the thermometer only changes if the temperature changes
No
No
Yes
Reliable but Not valid
Not reliable Not valid
Reliable and Valid
Complete the chart below
top related