A sample of 30 employees who work in the same office responded to a survey about how much time they spend commuting to work. The sample mean was 25 minutes and the sample standard deviation was 10 minutes. a Calculate the standard deviation of the population mean to the nearest tenth. (b) Use a 95% confidence interval to determine a range of values for the population mean. c) Write the 95% confidence interval in terms of the population mean plus or minus the margin of error. What does this represent in the situation?