H.3. Coronary heart disease (CHD) begins in young adulthood and is the fifth leading cause of death among adults aged 20 to 24 years. However, studies of serum cholesterol levels among college students are scarce. One study at a southern university investigated the lipid levels in a cohort of sedentary university students. A total of 108 students volunteered for the study and met the eligibility criteria. The following table summarizes the blood lipid levels, in milligrams per deciliter (mg/dl), of the participants broken down by gender:

Females (n=71) Males (n=37)

X s X s

Total Cholesterol 173.70 34.79 171.81 33.24

LDL 96.38 29.78 109.44 31.05

HDL 61.62 13.75 46.47 7.94

(a) Is it appropriate to use the two-sample t procedures to analyze these data for gender differences? Give reasons for your answer.

(b) Describe appropriate null and alternative hypotheses for comparing male and female total cholesterol levels.

(c) Carry out the significance test using = 0.05. Report the test statistic with the degrees of freedom and the P-value. summarize your conclusion.

(d) Find a 95% confidence interval for the difference between the two means. Compare the information given by the interval with the information given by the significance test.