13. For a population with a mean of p = 70, a score of X = 64 corresponds to z = - 1.50. What is the population standard deviation\"? 15. A normal distribution has a mean of p. = 54 and a standard deviation of cr = 6. a. b. What is the probability of randomly selecting a score less than X = 5]? What is the probability of selecting a sample of n = 4 scores with a mean less than M = 5 l ? What is the probability of selecting a sample of n = 36 scores with a mean less than M = 5] 'P