We select a random sample of 100 professional swimmers in the state of New Jersey and find out that the mean age is 20.8 years and standard deviation is 2.8 years. (a) calculate an 85% confidence interval. (b) Assume your null hypothesis is that the population mean age equals 21. Your alternative hypothesis is that the population mean age is greater than 21. Find the test statistic. (c) Assume a = significance level = 0.05. Do you reject your null hypothesis? ((d) Interpret your results in (a)