An observational study is done to see if eating at least two apples a week helps prevent tooth decay in children. However, the researchers are aware that children who eat apples may also drink less soda, so they measure soda consumption as well. In this example, soda consumption is an example of

Soft drink consumption is an example of a controlled variable.

Explanation:

A very important type of variable in the execution of an experiment is the controlled variable. This type of variable is not directly part of the experiment, but it is inevitably present in the experiment and must be measured, since its existence has a direct importance in the research results. This can be seen in the research above, where one wants to evaluate the effects of apple feeding on the incidence of caries. The consumption of soda is not part of the experiment, but its existence can influence the result, so it is a controlled cariavel and must be measured.

answer; genetics;