• Experiments are the only way to find a causal relationship

• One factor, the independent variable, causes a change in something else, the dependent factor

Hypothesis

• A prediction

  • An if/then statement

• If we manipulate the independent variable and everything else is constant, then the dependent variable will change because of the independent variables’ effect

• Holding everything else constant, so that there are no other factors changing the outcome, is called experimental control

Independent Variable

• Not everyone/everything receives the independent variable

• If everything is treated, how can you tell if it is working, and to what degree?

• Keeping a control that receives no treatment and knows they aren’t is important to compare

• It is also important to have a group who does not receive the independent variable but thinks they did

  • This can result in placebo, where participants report an effect believing it due to the independent variable

  • This determines how much of the treatment is psychological and how much is actual affects

• Other unintentional factors that may affect the dependent variable are called confounding factors

• For the best and most accurate data, participants should be randomly assigned to groups

Three Terms

• These three terms are often confused with one another

Random Sample/Random Selection

• Each person in a large population has equal chance of being chosen for the study

Representative Sample

• The group “looks like,” represents, the larger population

• Means that findings may be generalizable

Random Assignment

• Each participant has an equal change of being put into the experimental or placebo group

Control vs. Confounding Variables

• As control increases, confounding variables decrease

• You could conduct an experiment in a heavily controlled environment, but people do not live in a lab

  • By putting them in an unnatural environment, you are introducing a confounding variable: the potential for them to act differently

  • This poses a unique challenge to getting good data

The Experimental Method

• All experiments have…

  • A hypothesis

  • Independent variable

  • Dependent variable

  • Experimental group

  • Control group

  • Placebo group

  • Placebo

  • Random assignment

• Without these factors, experiments would rise validity and might sacrifice the ability to prove casualty