Click-through rates were measured for each of 83 mobile advertising campaigns, and showed an average rate of 2.38%, with a standard error of 0.134%. Please note that this is not a binomial situation because we are analyzing 83 percentage numbers and we do not know the size of each campaign. 

a. Find and interpret the two-sided 95% confidence interval. 

b. Find the two-sided 90% confidence interval. 

c. Find the one-sided 95% confidence interval that claims that the population mean click-through rate is at least some amount. 

d. Find the one-sided 99.9% confidence interval that claims that the population mean click-through rate is no larger than some amount.