A longitudinal study in apparently normal men is organized to relate changes in

Question

A longitudinal study in apparently normal men is organized to relate changes in cardiovascular risk parameters to subsequent mortality. The hypothesis being tested is that men whose cholesterol level rises have a different subsequent mortality than those whose cholesterol level drops. In particular, two groups of 50- to 59-year-old men with initially normal cholesterol levels are identified: (1) group A = 100 men whose cholesterol level rises by 50 mg/dL over a 5-year period, and (2) group B = 150 men whose cholesterol level drops by 50 mg/dL over a 5-year period. The groups are then followed for mortality over the next 5 years. The results are that in group A 20 men died and 6 men died in group B.

Using a 0.05 significance level, test for a difference in mortality between group A and group B.

Construct a 95% confidence interval estimate of the difference in mortality.

Explanation / Answer

Solution

Proportion died in Group A = 20/100 = 0.2

Proportion died in group b = 6/150 = 0.04

95% confidence interval : (0.20-0.04)+-1.96((0.20)(0.80)/100 + (0.04)(0.96)/150)0.5

= (0.0756,0.2444)

So we can conclude that there is difference in mortality between group A and group B

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