A veterinarian studying causes of enteroliths in horses suspects feeding too much alfalfa may be a culprit.

A veterinarian studying causes of enteroliths in horses suspects feeding too much alfalfa may be a culprit. The veterinarian hypothesizes that more than two thirds of all horses with enteroliths are fed mostly alfalfa. The veterinarian has access to horses that were examined at the veterinary clinic over the last five years. To find out about the diets of the horses it is necessary to contact the person responsible for feeding the horse prior to the diagnosis of enteroliths. This is time consuming and often it is not possible to contact the right person. It is more difficult the more time has elapsed.

Therefore, the veterinarian decides to only select the 30 horses diagnosed during the past 12 months, of which 23 were fed mostly alfalfa.

A z-test for proportions will be used to test the hypothesis.

This is:

a. appropriate because n > 30

b. appropriate because np0 10

c. appropriate because both np0​ 10 and n(1-p0)  10

d. not appropriate because n(1-p0) < 10