Question

identify which of these designs is most appropriate for the given experiment: completely randomized design, randomized block design, or matched pairs design. currently, there is no approved vaccine for the prevention of infection by west nile virus. a clinical trial of a possible vaccine is being planned to include subjects treated with the vaccine while other subjects are given a placebo. the most appropriate design is dropdown design.

Explanation:

In this clinical trial for a West Nile virus vaccine, subjects are randomly assigned to either the vaccine group or the placebo group. A completely randomized design involves randomly assigning participants to different treatment groups (here, vaccine or placebo) without blocking or matching, which fits this scenario as there's no mention of grouping by blocks or matching pairs. Randomized block design would involve grouping by a blocking variable first, and matched pairs design involves pairing similar subjects, neither of which is indicated here.

Answer:

completely randomized design