Amedical researcher wants to determine whether exercising can lower blood pressure. she recruits 100 people with highblood pressure to participate in the study. she assigns a random sample of 50 of them to pursue an exercise program thatincludes daily swimming and jogging. she assigns the other 50 to refrain from vigorous activity. she measures the bloodpressure of each of the 100 individuals both before and after the study. a. is this a controlled experiment or an observational study? b. on the average, the subjects in the exercise group substantially reduced their blood pressure, while the subjects in theno-exercise group did not experience a reduction. the researcher concludes that exercise decreases blood pressure. is thisconclusion better justified than the conclusion in exercise 8? explain.