You are interested to see if there is some truth to the statement \'an apple a d

Question

You are interested to see if there is some truth to the statement 'an apple a day keeps the doctor away.' We go to several randomly picked dentist offices in and around the Detroit area. Fifty clinic patients who report that they routinely eat an apple a day and 50 clinic patients who report that they eat less than one apple a week will be identified. The dentists will examine the patients and their records to determine the number of new cavities the patients have had over the past two years. They will then compare the number of new cavities in the two groups. Why is this an observation study and not an experiment? Explain the concept of confounding in the context of this study. Include an example of a possible confounding variable.

Explanation / Answer

(a) It is an observational study because the patients who arrive are observed and are not asked to perform anything. No experiment is included.

(b) A coufounding variable is an “extra” variable that you didn’t account for. They can ruin an experiment and give you useless results. Here a confounding variable can be age of the patient, the elder patients are expected to have more cavities than younger ones. So, a confounding variable here can be age.

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