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...

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 20​% of σ. Is this sample size​ practical?
σ
To be​ 95% confident that s is within
​1%
​5%
​10%
​20%
​30%
​40%
​50%
of the value of σ​, 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 σ​, the sample size n should be at least
​33,218
​1,336
336
85
38
22
14
The minimum sample size needed is