A veterinarian investigating possible causes of enteroliths in horses suspects t

Question

A veterinarian investigating possible causes of enteroliths in horses suspects that feeding alfalfa may be to blame. She wishes to estimate the proportion of horses with enteroliths who are fed at least two flakes of alfalfa per day. In a sample of 62 horses with enteroliths, she finds 42 are fed two or more flakes of alfalfa. A 95% confidence interval is calculated to be (0.561, 0.794). That interval has a margin of error of m = .1165. The veterinarian believes that this is too large and decides to use the current data as a pilot study to plan a proper study with a smaller margin of error of m = 0.05. She calculates the required sample size using = 0.678 to be n =

Explanation / Answer

here p=0.678

margin of error =0.05

and for 95% confidence interval ; z=1.96

hence sample size n=p(1-p)(Z/m)2 =336

hence option A is correct

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