Question

A normal population has mean 100 and variance 25. How large must the random sample
be if we want the standard error of the sample average to be 1.5?

I know the answer is 12. Would someone please be able to explain! and share what formula they used

Answer 1

so i found the equation SE = sigma/sqrt(n) I plugged in 1.5 for SE and 5 for sigma. i got n= 11.1 but that is not the correct answer..

Answer 2

Variance=25
Std Deviation = 5
so
1.5 = (5/sqrt(n)
n=11.11
then round up and
n=12