1. In a random sample of n = 31 randomly selected hospital stays for a heart attack, the mean number of days was = 4.8. The sample standard deviation was = 3 days. Follow the steps below to construct a 95% confidence interval for the population mean number of days staying in the hospital after a heart attack. (a) Calculate (round to at least 3 decimal places). (b) Since n = 31, degrees of freedom = (c) For a 95% confidence interval, find the critical t-value (t*). Use invT(area to the Left, df) if your calculator has it, or Table A.3 in the book. Round to 3 decimal places. (d) Use the formula = to calculate the margin of error. (Round to 3 decimal places.) (e) Once you have the margin of error, m, the endpoints confidence interval are ( , + ). Find a 95% confidence interval for the population mean number of days in the hospital. (f) Use the TInterval procedure on your calculator to check your answer. Give the calculator CI. Are the results about the same? (g) Interpret your confidence interval using the template on the notes page.