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?