Question

Assume that the sample is a simple random sample obtained from a normally distributed population of IQ scores of statistics professors. Use the table below to find the minimum sample size needed to be 95​% confident that the sample standard deviation s is within 30% of sigmaσ.

Is this sample size​ practical?

sigmaσ	To be​ 95% confident that s is within	​1%	​5%	​10%	​20%	​30%	​40%	​50%
	of the value of sigmaσ​, the sample size n should be at least	​19,205	768	192	48	21	12	8
	To be​ 99% confident that s is within	​1%	​5%	​10%	​20%	​30%	​40%	​50%
	of the value of sigmaσ​, the sample size n should be at least	​33,218	​1,336	336	85	38	22	14

Answer 1

Solution :

Minimum sample size corresponding to 95% confidence and 30% of = 21 .

Minimum sample size = 21

Sample size is not practical