Problem:
The association between job related exposure to welding fumes and chronic pulmonary disease (COPD) was explored in a cross-sectional study. The following data were reported for 399 COPD patients 37 currently work as welders; the remainder had no occupational exposure. Among 800 controls 48 were employed as welders
1. Construct the appropriate 2 X 2 table
2. Calculate the prevalence of persons exposed.
3. Calculate the prevalence of disease in persons not exposed
4. Calculate the prevalence rate.
5. Interpret the prevalence rate