a. A statistics practitioner calculated the mean and standard deviation

a. A statistics practitioner calculated the mean and standard deviation from a sample of 51. They are x? = 120 and s = 15. Estimate the population mean with 95% confidence.,b. Repeat part (a) with a 90% confidence level.,c. Repeat part (a) with an 80% confidence level.,d. What is the effect on the confidence interval estimate of decreasing the confidence level?