Scientific Method

Vocabulary Terms

HYPOTHESISThe part of an experiment where you make an educated guess or prediction as to what

will happen.

Your hypothesis should be written as an If…then…because statement.

Example:

If fertilizer is fed to tomato plants then the plants will produce larger tomatoes because the fertilizer helps the plant grow and produce bigger fruit.

CONTROL Part of an experiment that is not being tested

and is used for comparison.

No independent variable is applied.

Example

A tomato plant without fertilizer

This is what you will compare the experimental tomato plant to.

It is what will go untouched.

VARIABLES Factors that can affect

the outcome of an experiment.

There are 3 types of variables

constantsindependent variabledependent variable

CONSTANTS The variable(s) in an experiment that are

kept the same.

Examples

•Same amount of sunlight

•Same amount of water

•Same size and type of pot

•Same type of soil

INDEPENDENT VARIABLE

The experimental variable, or the variable that is changed or manipulated.

This is what you are testing, what you have control over. You can change or alter this variable in the experiment. Example:

If fertilizer is fed to a tomato plant then the plant will produce larger tomatoes because the fertilizer helps the plant grow and produce bigger fruit.

The fertilizer is the independent variable. You have control over whether it is added or not. It is the variable you are experimenting with or that you can change. It is the independent variable.

Helpful Reminder

The independent variable is always part of

the if portion of your hypothesis.

If fertilizer is fed to a tomato plant then the plant will produce larger tomatoes because the fertilizer helps the plant grow and produce bigger fruit.

Dependent variableThe variable that is effected by the independent variable.

DEPENDENT VARIABLEThe variable that is effected by the

independent variable.

This is the variable that you measure or observe during your experiment.

Example: If fertilizer is fed to a tomato plant then the plant will produce larger tomatoes because the fertilizer helps the plant grow and produce bigger fruit.

The tomato size is the dependent variable. The size of the tomatoes is effected by the fertilizer. Tomato size is the variable you are measuring and observing during the experiment.

The fertilizer which is the independent variable may or may not effect the size of the tomatoes.

Helpful Reminder

The dependent variable is always part of the then portion of your hypothesis.

If fertilizer is fed to a tomato plant

then the plant will produce larger tomatoes because the fertilizer helps

the plant grow and produce bigger fruit.

DATAThe information gathered and

recorded

Example

A line graph showing the daily growth of the tomatoes or a bar graph showing the mass of the

tomatoes

CONCLUSIONThe experimenter’s interpretation

of the results.

What happened?

Example

The addition of fertilizer had no effect on the size of the tomatoes.