In a study in UK, an association was found between sale of antiarrythmic drug and an increase in deaths due to asthma. This is an example of?

Ans. 'a' i.e., Ecological study Ecological studies (Correlation Studies) o Ecological study is an epidemiological study in which the unit of analysis is a population rather than an individual. o Therefore, ecological study utilizes data at the population level rather than the individual level. o The association between a disease and exposure is studied, e.g., there is a positive correlation between fat consuption an breast cancer in many nations. Conclusion is that fat consumption is a risk factor for breast cancer. o Ecological studies are valuable because they can be done easily and quickly by using population data that has already been collecting and seeking correlations between potential risk factor and various outcomes. o Ecological studies may be more appropriate than other designs when studying the impact of an exposure on a community level. o An ecological study is normally regarded as inferior to non-ecological designs such as case-control and Coho studies because it is susceptible to ecological fallacy. o Ecological fallacy occurs when conclusion are drawn about individuals from the data that are associated with groups, as relationship observed for groups may not necessarily hold for individuals. In this question association between sale of antiarrhythmic drug and increase in death due to asthma is given for general population of `UK' (not for individuals), so it is an example of ecological study. Other options, case control (case-reference) study, Coho study and experimental study (i.e., randomized controlled trials) have already been explained.