Experimental Methodology in AP Psychology

Purpose of Experiments
- Establish cause-and-effect relationships.
- Only scientific method capable of proving such relationships.

Hypothesis: A testable statement predicting the outcome of an experiment.
Operational Definitions: Clear definitions of how variables are measured or manipulated to ensure replicability.
Participant Selection: Process of choosing individuals for experiments.
Independent Variable (IV): The manipulated variable.
Dependent Variable (DV): The measured outcome affected by the IV.
Experimental & Control Groups: Groups used to compare the effects of the IV.
Confounding Variables: Uncontrolled variables that may influence the DV.
Random Assignment: Randomly placing participants into different groups to eliminate bias.
Placebo Control: Group receiving a fake treatment to measure the placebo effect.
Double-Blind Procedure: Neither participants nor experimenters know who gets the IV to reduce bias.
Statistical Significance (p-value): Measure of whether results are due to chance.
Replication: Repeating studies to verify results.

Develop a Hypothesis:
- Example: "If students attend lunchtime tutoring, then their grades will improve."
Distinguishing Experiments from Correlation:
- Experiments manipulate the IV and test the effect on the DV, whereas correlation observes existing relationships without manipulation.

Type I Error (False Positive): Incorrectly concluding a difference exists (e.g., believing boys perform better in math when they do not).
Type II Error (False Negative): Failing to detect an effect that is present (e.g., a test incorrectly showing a negative result for COVID).

Independent Variable (IV): Controlled by the researcher, impacts the DV.
Dependent Variable (DV): Measured effect due to changes in the IV, must have a quantifiable result.