Question

In one study on the effect of Dyazide on blood pressure level, 25 subjects were randomly chosen to receive Dyazide and 25 were chosen to receive a placebo. These subjects were later examined to check for differences in their blood pressure levels. In a second study, 200 subjects who reported taking Dyazide for a long period of time had their blood pressure levels compared with those of 200 people who had never taken Dyazide. Which of the following statements is correct?

Which of the following statements is correct?

The first study was a controlled experiment, while the second was an observational study.

Both studies were observational studies.

The first study was an observational study, while the second was a controlled experiment.

Both studies were controlled experiments.

Answer 1

Correct option:

The first study was a controlled experiment, while the second was an observational study.

EXPLANATION:

The first study was a controlled experiment because researcher tests a hypothesis, "Effect of Dyazide on blood pressure level" by looking for changes brought out by alterations. The second study was an observational study because the researcher has no control over the independent variable It is only analysis of data collected by 200 subjects who have been taking Dyazide for a long period of time and another 200 subjects who had never taken Dyazide.