Question

Whole grains $(4.2)$ A series of observational studies revealed that people who typically consume $3$ servings of whole grain per day have about a $20\%$ lower risk of dying from heart disease and about a $15\%$ lower risk of dying from stroke or cancer than those who consume no whole grains.

a. Explain how confounding makes it difficult to establish a cause-and-effect relationship between whole grain consumption and risk of dying from heart disease, stroke, or cancer, based on these studies.

b. Explain how researchers could establish a cause-and-effect relationship in this context.

Short answer

Part (a) Amount of exercise could be confounded the results.

Part (b) The people in the treatment group eat $3$ servings of whole grain per day, where the people in the control group do not eat whole grains at all.

Step-by-step solution

Part (a) Step 1: Given information

Persons who eat three servings of whole grains per day have a $20\%$ reduced chance of dying from heart disease and a $15\%$ lower risk of dying from stroke or cancer than people who don't eat any whole grains.

Part (a) Step 2: Explanation

When the effects of two variables on a response variable cannot be distinguished from one another, they are said to be confused.

It is impossible to establish a cause-and-effect relationship between whole grain consumption and the risk of dying from heart disease, stroke, or cancer since the results of the study could be contaminated by another variable.

For example, the quantity of exercise you get may affect your risk of dying from heart disease, stroke, or cancer, since if you exercise more, you'll be healthier and hence less likely to die from heart disease, stroke, or cancer. Although the amount of activity and whole grain consumption cannot be distinguished,

Part (b) Step 1: Explanation

If an experiment is used instead of observational research, a cause-and-effect link can be established in this setting. It may, for example, use a perfectly randomized experiment. In a truly randomized experiment, all individuals are assigned to a group at random. Choose a group of people and assign half of them to the treatment group, while the other half is assigned to the control group at random. The treatment group consumes three servings of whole grain per day, while the control group consumes no whole grains at all.