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9. According to a National Study, the mean serum high density lipoprotein (HDL) cholesterol of males 20-29 yeas old is 47. A doctor wants to estimate the mean serum HDL cholesterol of his 20-29-year-old patients. He randomly selects 15 of his 20-29-year-old patients and obtains the following data. Assume that o = 12.5. 48 61 46 35 48 34 64 42 29 71 64 47 56 27 53 a Use the data sample to calculate the sample mean serum HDL for the doctor's patients. b) Construct a 95% confidence interval for the doctor's patients. Construct a 99% confidence interval for the doctor's patients. Compare the differences between the two confidence Intervals