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


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?

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

 YoungOldMarginal Row Totals    

Developed18652020022065    

Developed Not6982298239805800109628782    

Marginal Column Totals6982484739826000109650847  (Grand Total)    

The Fisher exact test statistic value is < 0.00001.

The result is significant at p < .05.

answer: city needs 2.4 inches of rainfall more to match the record of 40 inches.

step-by-step explanation:

since we have given that

total annual rainfall a city record = 40 inches

this year, total rainfall recorded = 37.6 inches

number of inches of rainfall   is needed to match the record of 40 inches is given by

hence, city needs 2.4 inches of rainfall more to match the record of 40 inches.