Indicate whether the study is an observational study or a controlled experiment. A researcher was interested in the effects of exercise on academic performance in elementary school children. She went to the recess area of an elementary school and identified some students who were exercising vigorously and some who were not. The researcher then compared the grades of the exercisers with the grades of those who did not exercise.

The study is  an observational study.      

Explanation:

Observational study: In psychological research, the term "observational study" is described as a non-experimental yet empirical investigation associated with the effects that are being caused by a specific treatment. In other words, an observational study is determined as a study in which inferences is being drawn from a specific sample related to a particular population where an independent variable is not considered as under the control of the investigator due to logical constraints and ethical concerns.

In the question above, the given statement represents an observational study.

the branch of biology that deals with the normal functions of living organisms and their parts.

the way in which a living organism or bodily part functions.

for many centuries there were important factors which the economies of the muslim empires developed increasingly. they applied economic procedures in production, investment, finance, taxation and property. they used to tax certain goods (for example: harvest), they charged interest on money lent, they signed contracts with merchants; they relied on a common currency, and they used checks as well as promissory notes. with the money collected by means of taxation, the government provided the needy with an income. in addition, trading networks covered huge distances, so far regions started to have contact and exchange goods. this trade network covered areas of asia, africa and europe.