Chapter 4, Problem 3PT

To determine

To draw: The conclusion that could be drawn for the provided study.

Explanation of Solution

Given:

A study for angina has been conducted making the comparison of bypass surgery and use of drugs by looking at the medical records of the patients which were treated by one of the treatments. It was concluded that survival time of patients that was treated by drugs was maximum.

Here, the researchers are not influencing the outcome by randomly assigning the subjects to treatment or control groups, but instead observing the treatments. Therefore, the study is observational. So, many confounders are possible here. Thus, it cannot be concluded that drugs have prolonged life of the patients.

Hence, the correct option is (d).