A simple random sample of 120 vet clinics in the Midwest reveals that the vast majority of clinics only treat small pets (dogs,cats,rabbits,etc. )and not large animals (cows,horses,etc. ).Of the 120 clinics sampled,88 responded that they do not treat large animals at their clinic.What is a 90% confidence interval for p,the population proportion of vet clinics that do treat large animals?
A)(0.163,0.371)
B)(0.188,0.346)
C)(0.200,0.333)
D)(0.667,0.800)

Question

Quizplus · Accepted Answer

The sample proportion of clinics that do treat large animals is 32/120 = 0.267. Using the formula for a confidence interval for a proportion, the 90% confidence interval is calculated as 0.267 ± 1.645 * sqrt((0.267 * (1 - 0.267)) / 120), which results in the interval (0.200, 0.333).

A Simple Random Sample of 120 Vet Clinics in the Midwest