Variables in Scientific Experiments

&Writing Hypotheses

Independent Variable = “The Cause”

• The one thing the scientist changes in the experiment.

• The scientist controls this variable.• On a graph, it is on the x-axis (bottom).

Dependent Variable = “The Effect”

• The results of the experiment.• What the scientist measures!• On a graph, it is on the y-axis (vertical side)

Control Variables

• The variables the scientist keeps the same throughout the experiment.

• Remember—The only thing that can be different in an experiment is the independent variable.

Examples

The independent variable causes the dependent variable to change.

Example 1 in handout!

Example 2 in handout!

Example 3

3. Example: Lemon trees receiving the most water produce the largest lemons.

I=_______________ D=________________

How to Write a Hypothesis

• If_____then____ statement• If IV then DV because statement.

Example: Increased sleep may cause higher grades.

If __________________________________then____________________________________because____________________________________.