Which technique for gathering data (observational study or experiment) do you think was used in the following studies?

A) The Colorado Division of Wildlife netted and released 774 fish at Quincy Reservoir. There were 219 perch, 315 blue gill, 83 pike, and 157 rainbow trout.
B) The Colorado Division of Wildlife caught 41 bighorn sheep on Mt. Evans and gave each one an injection to prevent heart worm. A year later, 38 of these sheep did not have heart worm, while the other three did.
C) The Colorado Division of Wildlife imposed special fishing regulation on the Deckers section of the South Platte River. All trout under 15 inches had to be released. A study of trout before and after the regulation went into effect showed that the average length of a trout increased by 4.2 inches after the new regulation.
D) An ecology class used binoculars to watch 23 turtles a Lowell Ponds. It was found that 18 were box turtles and 5 were snapping turtles.

Observational study happens when you as a researcher observe the effects of a risk situation, a diagnosed test , a treatment or a an intervention without changing the subjects receiving the procedure.Example a case control study.

An experimental study happens when you as a researcher introduce an intervention to selected subjects and study the effects.In this study subjects are categorized by chance.i.e randomization is performed.

A. Observational study- number of different types of fish was observed after netting and releasing procedure.No fish was changed.

B.Experimental study----the effect was 38 sheep did not have heart worm while 3 had heart worm

C.Experimental study----After the regulation, the effect was an increase in length of trout fish by 4.2

D.Observational study-Turtles were observed through binoculars to identify the box turtles(18) and 5 snapping turtles.