Twenty Dogs and 20 Cats Were Subjects in an Experiment

Multiple Choice

Twenty dogs and 20 cats were subjects in an experiment to test the effectiveness of a new flea control chemical. Ten of the dogs were randomly assigned to an experimental group that wore a collar containing the chemical, while the others wore a similar collar without the chemical. The same was done with the cats. After 30 days the veterinarians were asked to inspect the animals for fleas and evidence of flea bites. This experiment is...

A) completely randomized with one factor: the species of animal
B) randomized block, blocked by species
C) randomized block, blocked by type of collar
D) completely randomized with two factors
E) completely randomized with one factor: the type of collar