Question

1.      Find the sample size to estimate a population mean within 95% confidence if the standard deviation is 6.2.

Answer 1

$Z_{95}=1.96$

$n=(\frac{Z_{95}\sigma}{0.5})^2=(\frac{1.96x6.2}{0.5})^2=590.7$

0.5 is a valid error. Usually 50%=0.5 is used, unless otherwise specified in the task.