Question

You are estimating the mean size of farms in New Hampshire. You want your 95% CI to have a margin of error of 25 acres. The standard deviation is 200 acres. How many farms to you have to measure?

Answer 1

Given

1-alpha =0.95

Alpha=0.05

Margine of error =E=25

Standard deviation =200

We know that

E=Z_alpha/2 *(standard deviation /sqrt(n))

n=(z_0.025)^2 *(standard deviation /E) ^2

=(1.96*1.96)*(200/25)^2

=245.86

=246

Number of farms require to measure is 246