This is case 1, in which the value of population standard deviation is assumed to be known. a. compute the standard deviation of the textbook price and assume this to be the population standard deviation. type this value in e5. b. pick a random sample of size 15. c. compute the mean of your random sample in e4 using the average function. d. calculate the standard error in cell e9 using the equation: s * √n. e. compute the z-statistic in cell e10 using the equation: (mean – 180) / s. e. f. compute the p-value for the lower tailed test in e13.