A simple random sample with n=56 provided a sample mean of 23.5 and a sample standard deviation of 4.5 . a. Develop a 90% confidence interval for the population mean (to 1 decimal). ( ) b. Develop a 95% confidence interval for the population mean (to 1 decimal). ( ) c. Develop a 99% confidence interval for the population mean (to 1 decimal). ( ) d. What happens to the margin of error and the confidence interval as the confidence level is increased