Experiments

Experiments

• Scientists use an experiment to search for cause and effect relationships.

• They design an experiment so that changes to one item cause something else to vary in a predictable way.

Experiments

• Variable = one of the things in an experiment that can be changed or controlled

Experiments

• A good experiment must…– Be able to be repeated– Change only one variable at a time

Experiments

• Scientists must be able to check each others work for accuracy.

• If more than one variable changes in an experiment, it may be difficult to find the variable that was responsible for the results.

Change Variable

• A variable that is changed by the scientist. • A good experiment has only one change

variable.• As the scientist changes this variable, he/she

observes what happens.• Also called the independent variable.

Responding Variable

• Scientist observes how the responding variable changes to the change made to the change variable.

• The responding variable is caused by or depends on the change variable.

• Also called the dependent variable.

Controlled variables

• Quantities that a scientist wants to stay constant.

• Sometimes called constant variables.

Control Group

• Control group = a group of subjects that is separated from the rest of the experiment where the change variable cannot influence the results

• Serves as a comparison group

Check for Understanding

• What happens to the other variables of the experiment that are not changing?

Check for Understanding

• Why do experiments need to be repeated?

Check for Understanding

• Why do simple experiments have only one variable that changes?