Question

estelles cornfield is divided into 6 regions. she wants to know if a new pesticide is as effective as the pesticide that she currently uses. she randomly assigns each of the 6 regions to either the new or current pesticide for a month, and shell compare the effectiveness of the pesticides.

what type of experiment design is this?

choose 1 answer:

a a randomized block design where the 6 regions are the blocks

b a matched pairs design with the new pesticide and current pesticide as the pairs

c a randomized block design where the pesticides are the blocks

d a completely randomized design

e a systematic cluster design

Explanation:

1. Recall experiment design types:

• Completely Randomized Design (CRD): Subjects (or experimental units, here the 6 regions) are randomly assigned to different treatment groups (here, new or current pesticide).
• Randomized Block Design (RBD): Experimental units are grouped into blocks (homogeneous groups) first, then treatments are randomly assigned within each block. Here, there's no blocking (grouping of regions into blocks) done—regions are just randomly assigned to treatments.
• Matched Pairs Design: Pairs of similar units are formed, and each unit in a pair gets a different treatment. Here, no pairing of regions is described.
• Systematic Cluster Design: Units are grouped into clusters, and clusters are randomly selected. Not applicable here as regions are assigned to treatments, not clusters selected.
• Option A: RBD needs blocks, but regions aren't blocked (just randomly assigned), so wrong.
• Option B: Matched pairs need pairing, which isn't done, so wrong.
• Option C: Pesticides can't be blocks (blocks are experimental units), so wrong.
• Option D: CRD fits—random assignment of 6 regions (experimental units) to 2 treatments (new/current pesticide).
• Option E: Cluster design doesn't apply here.

Answer:

D. A completely randomized design