A Recent Medical Study Found That People Who Drink More

Multiple Choice

A recent medical study found that people who drink more than four cups of coffee a day have more heart attacks than people who drink less coffee or no coffee. This led some doctors to suspect that coffee may be a contributing factor in causing heart attacks. However, more careful analysis of the data showed that heavy coffee drinkers tend to smoke more than other people. This is an example of

A) the placebo effect.
B) response error.
C) the double-blind technique.
D) a completely randomized design.
E) confounding.