From a Population That Is Normally Distributed with an Unknown

Multiple Choice

From a population that is normally distributed with an unknown standard deviation, a sample of size 20 elements is selected.To construct an interval estimate of the population mean, the proper distribution to use is the:

A) t distribution with 19 degrees of freedom
B) t distribution with 21 degrees of freedom
C) z distribution
D) standard normal distribution
E) none of the above