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

Question

Quizplus · Accepted Answer

When the population standard deviation is unknown and the sample size is small (n < 30), the t distribution is used to construct an interval estimate of the population mean. The degrees of freedom (df) for the t distribution are calculated as the sample size minus one (n - 1), which in this case is 20 - 1 = 19.

From a Population That Is Normally Distributed with an Unknown