Answer and Explanation

(A). stratified random sample

In the study, the veterinarians interested in investigating a possible link between enteritis, stones that form in the colon of horses, and diet. The veterinarians administer the feeding practices of horses by their owners in the hospital's state and divide them into sub-groups. Let us suppose we take 20 sub-groups each containing 10 horses. So, the treatment will be unbiased and every 5th owners of every horse is being treated at the hospital. Since it is a type of probability sampling, the unbiased condition is met and the sampling used is stratified random sampling.

Hence, Option(A) is the correct answer.

Explanation for the wrong answer

B. In simple random sampling, the sample is chosen at random which means each members of the population has same chance of being selected. This is not a case here.

C. In volunteer sampling, the researcher requests the respondents to join the sample, and the respondent decide whether to join or not. Thus, this is not the case here.

D. In Convenience sampling, the researcher chooses the sample that is readily available in some non-random way. Since it is cheap and easy way of gathering the data, so for generalized results, this type of sampling is not preferred.