A study was undeaken to find the relation between COPD and smoking. Patient's data was collected through records from government hospital and record of cigarettes sale from finance and taxation depaments. Study design?

Ecological Study also called Correlation Study Units of study:Population, Data can be used from populations with different characteristics Ecological Study Done at a point of time Done based on Secondary Data i.e. Collected data from records of hospital Data is not collected by Investigator himself. Used in Nutritional Surveys Cannot calculate strength of association / prevalence Unit of Study is population and results are extrapolated projected not on Individuals but on total population. This drawback is known as "Ecological Fallacy"