A study of peach trees found that the average number of peaches per tree was 625

Question

A study of peach trees found that the average number of peaches per tree was 625. The standard deviation of the population is 140 peaches per tree. A scientist wishes to find the 98% confidence interval for the mean number of peaches per tree. How many trees does she need to sample to obtain an average accurate to within 12 peaches per tree?

A) 137    B) 523    C) 622    D) 739

A study of peach trees found that the average number of peaches per tree was 625. The standard deviation of the population is 140 peaches per tree. A scientist wishes to find the 98% confidence interval for the mean number of peaches per tree. How many trees does she need to sample to obtain an average accurate to within 12 peaches per tree?

A) 137    B) 523    C) 622    D) 739

Explanation / Answer

we know that

E = z*s/sqrt(n)

it can be written as..
n = [z*s/E]^2

   here s=140 ,E=12 ,value of z at 98% confidence inervel = 2.33

  n= [ 2.33*140/12]^2

   =738.9336111

   answer is Option D

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