A Group of Students Asked Participants from Their School to See

Short Answer

A group of students asked participants from their school to see how many sit-ups they could perform in one minute. Subjects were then randomly assigned to drink either Sobe or Rockstar, two energy drinks. Rockstar is marketed primarily as an energy drink, whereas Sobe is advertised more for taste. Exactly 30 minutes later, the number of sit-ups in one minute was again recorded. The students conjectured that the increase in the number of sit-ups performed would be higher for students drinking Rockstar than for Sobe.
-Is this an experiment or an observational study?