In a study using 8 samples, and in which the population variance is unknown, the distribution that should be used to calculate confidence intervals is
A) a standard normal distribution.
B) a t distribution with 7 degrees of freedom.
C) a t distribution with 8 degrees of freedom.
D) a t distribution with 9 degrees of freedom.

Question

Quizplus · Accepted Answer

When the population variance is unknown and the sample size is small (less than 30), we use the t distribution. Since we have 8 samples, we have 8-1 = 7 degrees of freedom, making choice B the best option. The standard normal distribution (choice A) is used when the population variance is known or the sample size is large (greater than 30), and choices C and D have too many and too few degrees of freedom, respectively.

In a Study Using 8 Samples, and in Which the Population