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

Question

Quizplus · Accepted Answer

Confounding occurs when a variable (such as smoking) is associated with both the exposure (coffee consumption) and the outcome (heart attacks), making it difficult to determine the true effect of the exposure on the outcome. In this case, heavy coffee drinkers had more heart attacks not because of the coffee itself, but because they were more likely to smoke, which is a well-known risk factor for heart disease. The relationship between coffee consumption and heart disease is therefore confounded by smoking.

A Recent Medical Study Found That People Who Drink More