Question

Comparing exercise and risk of Coronary Heart Disease(CHD), total of 2326 registered women in study and divided into groups based on moderate exercise, strenuous exercise, and whether they developed some sort of CHD.

CHD NOT CHD TOTALS

Strenuous(SE) 65 1003 1068

Moderate(Not SE) 46 1212 1258

Totals 111 2215 2326

Using above table, find 90% confidence intervals for proportion of CHD in each group (eg. strenuous or moderate exercise). Do the confidence intervals overlap? What does this tell you about comparing the proportion of CHD for the two different groups, would you say they have different proportions?

Answer 1

Comparing exercise and risk of Coronary Heart Disease(CHD), total of 2326 registered women in study and divided into groups based on moderate exercise, strenuous exercise, and whether they developed some sort of CHD.

                       CHD NOT CHD TOTALS

Strenuous(SE)    65 1003 1068

Moderate(Not SE) 46 1212 1258

Totals 111 2215 2326

Using above table, find 90% confidence intervals for proportion of CHD in each group (eg. strenuous or moderate exercise). Do the confidence intervals overlap? What does this tell you about comparing the proportion of CHD for the two different groups, would you say they have different proportions?

Z value for 90% = 1.645

Strenuous group:

Confidence Interval Estimate for the Proportion
Data
Sample Size	1068
Number of Successes	65
Confidence Level	90%
Intermediate Calculations
Sample Proportion	0.060861423
Z Value	1.6450
Standard Error of the Proportion	0.0073
Interval Half Width	0.0120
Confidence Interval
Interval Lower Limit	0.0488
Interval Upper Limit	0.0729

90% CI for Strenuous group: (0.0488, 0.0729)

Non Strenuous group:

Confidence Interval Estimate for the Proportion
Data
Sample Size	1258
Number of Successes	46
Confidence Level	90%
Intermediate Calculations
Sample Proportion	0.036565978
Z Value	1.6450
Standard Error of the Proportion	0.0053
Interval Half Width	0.0087
Confidence Interval
Interval Lower Limit	0.0279
Interval Upper Limit	0.0453

90% CI for Non Strenuous group: (0.0279, 0.0453)

The two 90% confidence intervals for proportion of CHD are not overlapping. Therefore the we have enough evidence to conclude that CHD for the two groups are different proportions.