Chapter 9.1, Problem 1LC

In what circumstances is the t statistic used instead of a z-score for a hypothesis test?

a. The t statistic is used when the sample size is n = 30 or larger.

b. The t statistic is used when the population mean is unknown.

c. The t statistic is used when the population variance (or standard deviation) is unknown.

d. The t statistic is used it you are not sure that the population distribution is normal.