Suppose that a cohort study of body mass index and coronary heart disease (CHD) was undertaken. Participants were classified as having either a high or normal body mass index. Because age is associated with both body mass index and risk of CHD, age was considered a potential confounder and the age of each participant was recorded. The following data were gathered from the study participants: Normal Body Mass IndexHigh Body Mass Index DISEASEAGEDISEASEAGE STATUSYoungOldSTATUSYoungOld Developed1865Developed20200 CHDCHD Did Not69822982Did Not39805800 Develop CHDDevelop CHD Total70003000Total40006000 1) Set up the two by two to evaluate the crude association between body mass index and CHD and calculate the crude risk ratio? 2) Set up the two by two tables to evaluate the relationship between body mass index and CHD stratified by age. That is, calculate the risk ratios separately for the young and old participants? 3)Is age a confounder in this study? How do you know?
Accepted Solution
A:
Answer:Step-by-step explanation:Using the formula
Equation
Where:
Sample 1 Proportion (or total number)
69824847
Sample 1 Size (N1)
70003000
Sample 2 Proportion (or total number)
39826000
Sample 2 Size (N2)
40006000
Significance Level: 0.05
Two-tailed
We have
The value of z is 173.1037. The value of p is < .00001. The result is significant at p < .05.
3)
Results
Young Old Marginal Row Totals Developed 1865 20200 22065 Developed Not 69822982 39805800 109628782 Marginal Column Totals 69824847 39826000 109650847 (Grand Total)
The Fisher exact test statistic value is < 0.00001. The result is significant at p < .05.