Final answer:
A within-subjects design involves each participant experiencing all conditions, allowing for the study of changes within individuals by controlling for lurking variables through random assignment. Measurements of the dependent variable are taken after each condition to observe effects of the independent variable.
Step-by-step explanation:
In a within-subjects design, each participant serves in all experimental conditions. This type of design is instrumental in studying changes within individual participants, as opposed to comparing different groups. By having each participant experience every condition, researchers eliminate between-group differences and instead focus on within-subject variability. Randomly assigning the order in which participants receive treatments helps to control for order effects and potential lurking variables. Typically, the dependent variable is measured after every condition to observe the effect of the independent variable.
A control or placebo condition is often used to establish a baseline for comparison. This ensures that any observed effect can be attributed to the experimental manipulation. In some well-controlled experiments, researchers and participants may be blind to condition assignments to prevent biases. This is known as a double-blind study. By meticulously controlling for external factors and ensuring the manipulation of only the independent variable, researchers can deduce cause-and-effect relationships.