(a) Using the sample data, what is the margin of error in dollars associated with a 95% confidence interval? Since the population standard deviation is known, the normal distribution will be used in the calculation of the margin of error, E. E=z/2n The value of z/2 is the z value corresponding to an upper tail area of 2 and a confidence level of 1. Common values for z/2 for various confidence levels are given below. According to the table, for a 95% confidence level, the necessary value for z//2 is The survey was conducted among a sample of 59 discount brokers, and we are to assume a known population standard deviation of 514. Therefore, n= and =