A study of treatments for angina (pain due to low blood supply to the heart) compared

bypass surgery, angioplasty, and use of drugs. The study looked at the medical records

of thousands of angina patients whose doctors had chosen one of these treatments. It

found that the average survival time of patients given drugs was the highest. What do

you conclude?

a. This study proves that drugs prolong life and should be the treatment of choice.

b. We can conclude that drugs prolong life because the study was a comparative

experiment.

c. We can’t conclude that drugs prolong life because the patients were volunteers.

d. We can’t conclude that drugs prolong life because the groups might differ in ways

besides the treatment.

e. We can’t conclude that drugs prolong life because no placebo was used.

We have been given four options from which we have to select the correct one.

a. This study proves that drugs prolong life and should be the treatment of choice.

b. We can conclude that drugs prolong life because the study was a comparative

experiment.

c. We can’t conclude that drugs prolong life because the patients were volunteers.

d. We can’t conclude that drugs prolong life because the groups might differ in ways

besides the treatment.

e. We can’t conclude that drugs prolong life because no placebo was used

An observational research attempts to collect data without disrupting the scene being observed.

As a result, we can deduce that the study in question makes use of records and is thus an observational study.

An observational study cannot conclude cause and effect (an experiment is required), because observational studies always involve the possibility of confounding variables (as some variables not included in the study could influence the results without us knowing it).