Question

A 95% CI for a normal population with known std dev produces margin of error of 0.004 based on a sample size of 100. If we wish to halve the margin of error, how large a sample must we take?

Answer:?

Answer 1

We know margin of error:

E=

0.004= (at 95% confidence interval Zc=1.96)

0.004=

=0.020408

Now according to question, we have to find the sample size for which margin of error becomes half

=19.95

n=19.95²

n=398

please rate my answer and comment for doubts.