Experimental Designs

Key Concept: Different participants are used in each condition (1 condition per person).
Memory Aid: Independent = Individual groups that are totally separate.
ADVANTAGES:
- No order effects: Participants are tested only once, so no practice, fatigue, or boredom.
DISADVANTAGES:
- Participant variables: Individual differences between groups (e.g., age, IQ) may skew results.
Control Strategy:
- Random Allocation: Pull names from a hat to ensure every participant has an equal chance of being in any condition.

Key Concept: The same participants take part in all conditions.
Memory Aid: Repeated = Repeat performance by the exact same people.
ADVANTAGES:
- Controls participant variables: Individual differences are eliminated because the same people are compared across conditions.
DISADVANTAGES:
- Order effects: Performance in later conditions may suffer (fatigue/boredom) or improve (practice).
Control Strategy:
- Counterbalancing (AB/BA): Half of the participants do Condition A then B, while the other half do Condition B then A to balance out order effects.

Key Concept: Participants are paired on key traits (e.g., age, IQ), then one member of each pair is randomly assigned to a separate condition.
Memory Aid: Matched = Matching twins split into separate groups.
ADVANTAGES:
- No order effects: Each participant is tested only once.
- Reduces participant variables: Key traits are held constant across conditions.
DISADVANTAGES:
- Time-consuming and complex: Hard to match people accurately; requires pre-testing and more participants.
Control Strategy:
- Pre-tests: Conduct initial testing to accurately pair participants on key criteria before allocation.

Independent Groups: Different people $\rightarrow$ Problem: Participant Variables $\rightarrow$ Fix: Random Allocation
Repeated Measures: Same people $\rightarrow$ Problem: Order Effects $\rightarrow$ Fix: Counterbalancing
Matched Pairs: Paired people $\rightarrow$ Problem: Time/Difficulty $\rightarrow$ Fix: Pre-testing