Q U E 5 TI D H B The reason for using the t-distn'bution in a hypothesis test about the population mean is: C} a. the population standard deviation is unknown. 0 l1 it results in a lower probability of a Type I error occurring. 0 '3' it provides a smaller critical value than the standard normal distribution for a given sample size. 0 d- the population is not nonnallv distributed