Chpt8 how to do an experiment

L.O: students will review how to conduct controlled experiments.

Do now: read your

“cheat sheet”

How to design a controlled

experiment:

Diet pill commercials use “before and after” shots as a side by side comparison to show that the pills REALLY work!

before After!

When they ask if you want to

“supersize it”, say NO!!!!

Scientists conduct controlled experiments as side by side comparisons too!!!!!!

A controlled experiment ALWAYS has at least TWO groups: an experimental group and a control group.

BOTH groups are IDENTICAL GROUPS…but

• only the experimental group gets the drug (or the treatment).

• The control groups doesn’t get the drug (or the treatment).

• Sometimes the control group is given a placebo (a fake drug or a sugar pill)

Experimental group gets the drug or the treatment.

Control group is identical to experimental group but DOES

NOT get the drug or treatment!

The two groups are compared to see IF the drug or treatment REALLY works!!!!!!

a good experiment must have a large number of test subjects, be repeatable &

take place for a long time!!!!!!

Characteristics of a good experiment:

1. Has both an experimental group and a control group.

2. Has many many test subjects.3. Is repeated many many times.4. The experiment lasts for long time (weeks, months,

years…)

An old saying says: “A picture is worth a thousand words”….

Scientists use graphs and tables because they make complicated data, easier to understand.

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You MUST be able to read a table and a graph!

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You MUST be able to draw a graph from a data table!

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In many experiments are looking for cause and effect relationships….

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IF one thing CAUSES something ELSE.

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Experiments have independent variables and dependent variables:

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independent variables are the cause.

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dependent variables are the effect.

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experiments are designed to see IF the independent variables causes the dependent variable to happen.

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in data tables: the independent variable is ALWAYS the first column

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in graphs: the independent variable is ALWAYS the X-axis

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in graphs: the dependent variable is ALWAYS Y-axis.

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you must be able to draw conclusions from tables and graphs.

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Now answer 1-20.

The scientific method:

The scientific method:

The scientific method is a method of designing an experiment.

A well-designed experiment has the following:

• A problem: written as a question.• Materials:• A hypothesis: (a possible answer to the problem): MUST BE

WRITTEN AS AN “IF-THEN STATEMENT (NOT as a question).• The “IF” is the independent variable (the cause), the “THEN” is

the dependent variable (the effect)• Procedure: what will be done to prove or disprove the hypothesis.• Observations: the collected data.• Tables and graphs: used to display and help interpret the results.• Conclusions: was the experiment VALID , did the results support or

refute the hypothesis?

A valid experiment is one where the data and conclusions support the hypothesis.

The hypothesis was valid (correct)!

Now answer 21- 49

You MUST know how to draw line graphs. There WILLLLLLLLLL definnnnnntellllly be one on the regents!!!!

How to draw a line graph, using data from a table:

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1. Label the X-axis (ALWAYS the independent variable) label the Y-axis (ALWAYS the dependent variable)

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2. Make an appropriate scale number line for the X-axis. the units MUST be EVENLY spread out! (0,1,2,3,4 …or 0, 2,4,6,8…or 0,5, 10,

15…. Or 0, 10,20,30…or 0.0,0.5,1.0, 1.5, 2.0, 2.5….)

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3. Make an appropriate scale number line for the Y-axis. the units MUST be EVENLY spread out! (0,1,2,3,4 …or 0, 2,4,6,8…or 0,5, 10,

15…. Or 0, 10,20,30…or 0.0,0.5,1.0, 1.5, 2.0, 2.5….)

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4. Accurately plot the points.

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5. connect the points. Surround each point with a small circle,

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Now answer 50- 82.

You probably WON’T have to draw a bar graph BUT you must know how to read them!!!!

Example: predict how much this country’s population will grow in 2003.

Now answer 83- 108

Now: complete all the unfinished questions!

Make me proud!