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# Journal 10/10/13 - PowerPoint PPT Presentation

Journal 10/10/13. A man is testing the effects of a drug on lab mice. They feed some mice 10 mg of the drug, others 20 mg of the drug, and still others no drug. Which group of mice are the control?. Objective Tonight’s Homework. To see applications for control variables.

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### Journal 10/10/13

A man is testing the effects of a drug on lab mice. They feed some mice 10 mg of the drug, others 20 mg of the drug, and still others no drug. Which group of mice are the control?

Objective Tonight’s Homework

To see applications for control variables

### Notes on Control Variables

Control variables can come into an experiment in two ways:

1) Scientists will sometimes have a setup called a ‘control’, where they run the experiment just ‘as is’ without changing anything.

This way, if something changes about the control, we know that we’ve accidentally introduced a new variable into the experiment

### Notes on Control Variables

Control variables can come into an experiment in two ways:

1) Scientists will sometimes have a setup called a ‘control’, where they run the experiment just ‘as is’ without changing anything.

This way, if something changes about the control, we know that we’ve accidentally introduced a new variable into the experiment

2) Scientists can specifically control a single variable. If you’re testing sniper rifles for range, you’ll test indoors to specifically cut out wind as a variable.

### Notes on Control Variables

Examples:

There was once an experiment where some scientists wanted to see the effect of estrogen on rats. They set up a control where the rats weren’t fed estrogen.

However, after a while they found that all the rats were behaving as if they had been given estrogen.

They looked at the control and found they were getting estrogen from the plastic in the water bottles. Without the control, they never would have found this.

### Notes on Control Variables

Examples:

Mythbusters:

They did an episode where they were testing is a dropped bullet would hit the ground at the same time as a fired bullet.

They did the test indoors to cut out wind as a variable. In this instance, they specifically controlled that variable.

### Designing a Lab for Variables

Mr. C. wants you to learn your types of variables well.

To do this, you’re going to design and run an experiment in class. It can be any experiment as long as it’s something we have the parts for in class.

Later this week, you’ll isolate variables and things for this experiment, but for today, all you need to do is design what your experiment is going to be.

### Exit Question #25

How do we define a control variable?

a) Something that we keep from changing

b) Something that only changes some of time

c) Something that changes all the time

d) Something that can’t change

e) Something that has to change

f) None of the above