In a repeated measures experimental design:
a. Subjects’ behavior is measured multiple times under one condition before doing the same under a comparison condition.
b. Control and treatment conditions are repeated to assess reliability.
c. Subjects’ behavior is measured multiple times under each condition simultaneously.
d. Subjects’ behavior is measured repeatedly to generate sufficient data for analysis.
The correct answer and explanation is:
Correct answer: a. Subjects’ behavior is measured multiple times under one condition before doing the same under a comparison condition.
Explanation (≈300 words):
A repeated measures experimental design is a type of within-subjects design in which the same participants are exposed to all conditions of the experiment. This design is commonly used in psychology, medical trials, and behavioral studies because it helps control for individual differences—each participant acts as their own control.
In option (a), the key feature is described accurately: the same subjects are measured multiple times under one condition before being measured again under a different (comparison) condition. This allows researchers to compare how the same individual responds to different conditions, improving the sensitivity of the experiment and reducing the error variance caused by differences between individuals.
Why the other options are incorrect:
- (b) Control and treatment conditions are repeated to assess reliability:
While repeated measures can help assess reliability, this option misrepresents the structure of the design. It’s not the conditions that are repeated, but rather the measurements of the same subjects under each condition. - (c) Subjects’ behavior is measured multiple times under each condition simultaneously:
It’s not possible to expose subjects to multiple conditions simultaneously in a meaningful experimental setup. Repeated measures involve sequential exposures, not simultaneous ones. - (d) Subjects’ behavior is measured repeatedly to generate sufficient data for analysis:
While repeated measurement does increase data quantity, this statement is too vague and does not capture the core structure of comparing conditions within the same subjects, which defines a repeated measures design.
In conclusion, option (a) most accurately describes the structure and intent of a repeated measures design: tracking individual behavioral changes across different conditions by testing the same participants multiple times.