A veterinarian interested in studying the causes of enteroliths in horses suspects that a diet high in alfalfa may be a cause. The veterinarian decides to use the following design: identify 30 horses at high risk for enteroliths, and divide them into 10 groups of 3 horses. Some groups consist of horses in barn stalls, some groups consist of horses in outdoor paddocks, and some groups consist of horses in pastures. Within each group, one horse is randomly assigned to an alfalfa diet, one is assigned to a grass hay diet, and one horse is fed oat hay. When a horse is in a pasture, all the other horses in that pasture will also receive the diet of the study horse. Therefore, only one horse could be selected from a given pasture. The blocking is done:
A)to reduce the potentially confounding effect of comparing more than two treatments.
B)to reduce the potentially confounding effect that the type of housing may have.
C)to increase the treatment effects.
D)All of the answer options are correct.

Question

Quizplus · Accepted Answer

Blocking is done to reduce the potentially confounding effect that the type of housing may have. By dividing the horses into groups based on their housing environment, the researcher can control for any housing-related factors that may affect the development of enteroliths, such as differences in exercise levels or access to different types of feed. This increases the internal validity of the study. Choice A is not correct because the design does not involve comparing more than two treatments. Choice C is not correct because blocking does not increase treatment effects. Choice D is not correct because not all answer options are correct; only B is correct.

A Veterinarian Interested in Studying the Causes of Enteroliths in Horses