You can use both the t statistic and the z statistic to test hypotheses about the mean of population. The test that uses the t statistic is typically referred to as a t test, while the test that uses z statistic is commonly called a z test. Which of the following statements are true of the t statistic? Check all that apply.

a. If you know the population standard deviation, you should use the t statistic.
b. The t statistic could be considered as an estimated z statistic.
c. The t statistic provides a relatively poor estimate of z with small sample sizes.
d. The formula for the t statistic is t = (M - s) / SM.