A random sample of n measurements was selected from a population with unknown mean p and standard deviation o = 35 for each of the situations in parts a through d. Calculate a 90% confidence interval for p for each of these situations. a. n = 75, x =22 b. n = 150, x = 111 c. n = 120, x = 13 d. n = 120, x =4.53 e. Is the assumption that the underlying population of measurements is normally distributed necessary to ensure the validity of the confidence intervals in parts a through d? Explain. a. ( (Round to two decimal places as needed.)