School Girls

Could someone help me get started on this problem?

How large a sample of school girls having a standard deviation of 25 points in their IQ scores would be needed to estimate the mean IQ score u within + or - 5 points with 95% confidence?


TS Contributor

An example of this type of problem can be found in our Examples section. The post is titled "Determining Sample Size."



TS Contributor
Yes, if you use the formula that does not consider power, then you get:

n = Z^2 * (s^2/d^2)

= (1.96)^2 * (25^2 / 5^2)

= 96.04

Round up to 97.