Question

1. The dentists in a dental clinic would like to determine if there is a difference between the number of new cavities in people who eat an apple a day and in people than one apple a week. They are going to conduct a study with 50 people in each group. who eat less 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. (a) Why is this an observational study and not an experiment? (b) Explain the concept of confounding in the context of this study. Include an example of a possible confounding variable.

Answer 1

a) in experimental study, the researcher intervenes in the actions of the subjects thereby controlling the variables that are studied. But in observational study. The researcher doesn't have any control over the variable. In this study also, the researcher is merely observing the different outcomes from two groups. They are not making the subjects eat fixed number of apples or causing any other change in routine that can affect the variable under observation, that is the number of cavities. So, this is an observational study.

b) Dental hygiene is a confounding variable. The individuals who regularly eat apple a day are the ones follow a particular diet and do all routines as recommended by doctor. So, they are expected to have better dental hygiene as the maintain that also, as a part of their routine. On the other hand, the group of people who eat less that one apple a week can be considered as the ones with a more casual approach and hence are likely to have lesser dental hygiene and hence more cavities. So, this is a confounding variable.