Background In the small island nation of Epidoria a team of

Background - In the small island nation of Epidoria, a team of reproductive epidemiologists has been studying the relationship between very low birth weight and risk of cognitive, motor, and behavioral problems. Five years ago these investigators initiated a study. Using birth certificate files and delivery room entry logs, these investigators attempted to identify all full-term births in Epidoria over a 6-month period. The investigators enrolled all low birth weight babies and a representative sample of normal birth weight babies into their study. The investigators then examined the children every year until age 3 years. During the last examination, the investigators administered a standardized developmental screening test to assess personal-social, language, and motor-adaptive skills. Based on this test, the investigators classified the children into two groups: normal development and delayed development.

The results from the study were:

What kind of a study is this? What is the exposure under study? What is the outcome under study?r

Solution

The above contingency table is an example of observaional study. Here one is interested for the association between the values of two categorical variables collected for each unit. The different kinds of bisrth weights and two different kinds of develovement are the exposure of the study.