Question

A dermatologist will conduct an experiment to investigate the effectiveness of a new drug to treat acne. The dermatologist has recruited 36 pairs of identical twins. Each person in the experiment has acne and each person in the experiment will receive either the new drug or a placebo. After each person in the experiment uses either the new drug or the placebo for 2 weeks, the dermatologist will evaluate the improvement in acne severity for each person on a scale from 0 (no improvement) to 100 (complete cure).

Each twin in the experiment has a severity of acne similar to that of the other twin. However, the severity of acne differs from one twin pair to another.

(a) For the dermatologist's experiment, describe a statistical advantage of using a matched-pairs design where twins are paired rather than using a completely randomized design.

(b) For the dermatologist's experiment, describe how the treatments can be randomly assigned to people using a matched-pairs design in which twins are paired.

Answer 1

a) The advantage of a matched-pairs design in the dermatologist's experiment is to control for genetic and environmental variables, making the results more likely attributable to the treatment.

b) The treatments are randomly assigned within each twin pair to avoid bias and ensure that the difference in treatment is the only variable.

Step-by-step explanation:

a) The statistical advantage of using a matched-pairs design where twins are paired in the dermatologist's experiment is that it accounts for potential confounding variables that are related to the genetics and the environment of the participants.

Since identical twins share the same genetic makeup and usually the same environment, differences in acne severity due to these factors are minimized.

Therefore, any observed differences in acne severity after the treatment are more likely to be attributed to the effectiveness of the new drug or placebo.

b) In a matched-pairs design with twins, the dermatologist can randomly assign the treatments to ensure each twin in a pair receives a different treatment (one gets the new drug and the other gets the placebo).

This random assignment is typically done by flipping a coin or using a computer-generated random sequence.

By doing so, the treatment allocation is unbiased, and the influence of the researcher's preferences on the assignment is eliminated.