School Girls

[Jerryberry]

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?

[JohnM]

Jerry-

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

John

[Jerryberry]

Thanks again.

[Jerryberry]

I came up with an answer of 97 school girls

[JohnM]

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.