When calculating the confidence interval for the mean when the standard deviation is known, a distribution is used. However, when the standard deviation is unknown, a distribution is used. Select one: O a z; F O b. t;z O c. z; t O d. tz For the following four questions, utilize the following information: The population standard deviation is unknown. The sample mean = 46; s = 15; n = 25. What distribution would you use to calculate the confidence interval? Select one: a z b. t O C F Clear my choice n O c. F Clear my choice What is the estimate of the standard error of the mean? Select one: O a. 0.6 Ob. 3 C. 0.33 d. 15 What are the number of degrees of freedom? Select one: O a. 25 Ob 24 O c. 26 Od. 14 m