Lias conducted an experiment about the effects of exercise on the heart rate of teenagers. Before morning basketball practice, he asked the members of his high school team to be his subjects. He measured each of their heart rates before and after a set of exercises. Which change would most reduce the bias of his experimental design?

Test the team members on the same exercises after practice too.

Test additional boys as well as several girls from different classes.

Test girls from his school, as well as teachers, siblings, and family friends.

Test the team members every day for a week to increase data.

In the given case, there is a need to ensure that the exercise is very well monitored. However, in my opinion, the most essential characteristic he requires to change is the people. First of all, all the subjects are of a school sports team, therefore, they all would be fit, and they are all about the same age group.

Thus, the results would vary if the level of fitness, the age of teenagers, and sex differ. It is thus, essential to record the outcomes from a wide array of individuals in order to reduce the bias of the experimental design in the given case. Therefore, testing additional boys as well as several girls from different classes would be appropriate in the given case.

Test additional boys as well as several girls from different classes.

Explanation:

Tests the members of the same class will not represent different data and that makes it possible to compare the results to form a correct and efficient conclusion. In this case, the conclusion of the experiment may be presented incorrectly, with a strong presence of bias.

For this reason, the idea would be that Lias reduced the possible bias, testing additional boys, as well as several girls from different classes. This way, he would have a variety of data that could be compared and form an efficient conclusion.