Question

does a platelet - rich plasma (prp) injection into the scalp promote hair growth? researchers identified 50 female patients with female pattern hair loss. the patients ranged in age from 30 to 60 years. for each patient, two areas with hair loss were identified. a coin toss was used to decide which area received the prp injection and which received a saline injection. injections were given to each patient at one - week intervals. after 6 months the change in the patients hair density (number of hairs per square centimeter) and hair diameter (millimeters) was measured. the mean difference in hair density (pcp minus saline) was 64.41\\(\frac{hairs}{cm^{2}}\\) and the mean difference in hair thickness was 0.07 mm. complete parts (a) through (g) below. (a) what type of experimental design is this? ○a. randomized block design. ○b. case - control study ○c. cohort study ○d. matched - pairs design ○e. completely randomized design

Explanation:

• Matched - pairs design: In this study, for each patient (the "pair"), two areas (one receiving PRP and one receiving saline) are compared. This is a classic example of a matched - pairs design where each individual serves as their own control.
• Randomized block design: Usually has blocks (groups) of experimental units, and random assignment within blocks. Here, it's not about blocks of patients but paired areas within each patient.
• Case - control study: Is an observational study (retrospective) where cases (with a condition) and controls (without) are compared. This is an experiment, not an observational study.
• Cohort study: Follows a group (cohort) over time. This is an experiment with two treatments on the same patient.
• Completely randomized design: Would randomly assign patients to two different groups (e.g., all of one group gets PRP and the other gets saline). But here, each patient gets both treatments (in different areas).

Answer:

D. Matched - pairs design