A skin-care company tests a new lotion against a competitor by applying one lotion to each subject's left cheek and the other to the right cheek (with side randomized). After 4 weeks, dermatologists rate skin smoothness on each cheek.
Which design is described?
- A
Observational study
- B
Completely randomized design
- Ccheck_circle
Matched-pairs design
- D
Randomized block with multiple blocks per subject
Explanation
Each subject receives both treatments simultaneously, with side randomized; each subject is the matched pair. Comparisons within subjects control for individual skin differences.