A fitness instructor wants to test the effectiveness of a performance-enhanding herbal supplement on students in her exercise class. To create experimental groups that are similar at the beginning of the study, the students are assigned into two groups at random (they cannot choose which group they are in). Students in both groups are given a pill to take every day, but they do not know whether the pill is a placebo (sugar pill) or the herbal supplement. The instructor gives Group A the herbal supplement and Group B receives the placebo (sugar pill). The students' fitness level is compared before and after sik weeks of consuming the supplement or the sugar pill. No differences in performance ability were found between the two groups suggesting that the herbal supplement was not effective. Is this an example of an observational study or an experimental study? Why?

In case of an experimental study the researcher first defines the variable of interest. Then the researcher studies this variables by applying different treatments.

A very basic form of conducting an experimental study is to divide the sample selected into two groups; one is the treatment group and the other is the control group. The treatment group is given the actual treatment and the control group is given a placebo.

Then the researcher studies the effect of treatment and placebo on the sample.

In this case the variable of interest is performance ability and the treatment is the performance-enhancing herbal supplement. The placebo provided are sugar pills.

The fitness instructor studies the effect of performance-enhancing herbal supplement on the performance ability of the students and the effect of sugar pills on the performance ability of the other group of students.

The result of this experiment is that there is no difference in the performance ability after providing the treatment and placebo.

Thus, this is an example of experimental study.