Question

How do we tell whether a population is normally distributed or approximately normal when the population standard deviation is unknown?

Answer 1

solution:

in general population is normally distributed or approximately normal can be known by the sample size.

when sample standard deviation is unknown ,and the underlying population is normally distributed and we can assume the distribution of the sample mean is normally distributed  then we can use the t distribution to estimate the population mean

so we can tell the population is normally distributed or approximately normal by sample mean