Chapter 10: Simple Experiments Flashcards

Purpose of Simple Experiments

Designed to test causal claims by manipulating an independent variable (IV) and measuring a dependent variable (DV).
Must satisfy the three criteria for causation:
- Covariance – changes in IV are associated with changes in DV. Example: People who get more sleep (IV) tend to score higher on memory tests (DV).
- Temporal Precedence – IV must come before DV. Example: You manipulate whether someone studies in a quiet or noisy room, then test their performance.
- Internal Validity – no alternative explanations (confounds) for the outcome. Example: Random assignment ensures groups were equal before the manipulation.

Independent Variable (IV): What the researcher manipulates. Example: Type of lighting in a room (dim vs. bright).
Dependent Variable (DV): What the researcher measures. Example: Number of words recalled in a memory test.
Control Variables: Kept constant to ensure valid results. Example: All participants are tested at the same time of day.

Treatment Group – receives the experimental condition. Example: Gets a new teaching method.
Control Group – receives standard or no treatment. Example: Uses traditional teaching method.
Placebo Group – receives a fake or inactive treatment. Example: Sugar pill in a drug study.

Design Confound: A variable that accidentally changes along with the IV. Example: All participants in the “dim light” condition also had music playing—can't tell if light or music affected performance.
Selection Effects: Groups differ systematically at the start. Example: Students who self-select into morning vs. evening classes may differ in motivation.
- Solution: Use random assignment or matched groups.
Unsystematic Variability: Random variation that isn’t consistent. Example: Mood differences across participants may add noise but not bias.

Independent-Groups Design: Different people in each condition. Example: One group tries a new diet, another sticks to their usual routine.
Within-Groups Design: Same participants experience all conditions. Example: Everyone tries both diet plans, one after the other.
Posttest-Only Design: DV measured after the manipulation only. Example: Participants read a persuasive message (IV) → rate their attitude (DV).
Pretest/Posttest Design: DV measured before and after manipulation. Example: Measure attitudes before and after a workshop on diversity.

Note-Taking Study (Mueller & Oppenheimer):
- Compared laptop vs. longhand note-taking.
- Longhand note-takers scored better on conceptual questions.
Pasta Bowl Study (Wansink et al.):
- Larger bowls = people served and ate more pasta.
Violent Video Game Study:
- Participants played a violent or non-violent video game, then measured aggression using a noise-blast task.
- Those in the violent game condition showed more aggressive behavior.