Question

the difference between an observational study and an experiment is that
○ in an observational study, only one group is studied, and in an experiment, two groups are studied.
○ in an observational study, the researchers do not control treatment, and in an experiment, they do.
○
○ in an experiment, one group is studied over a short period of time, and in an observational study, the group is studied
over a longer period of time.

Explanation:

To determine the difference between an observational study and an experiment, we analyze each option:

• The first option is incorrect because both observational studies and experiments can study one or more groups.
• The second option is correct. In an observational study, researchers observe and measure without controlling the treatment (e.g., observing the effect of smoking on health without intervening). In an experiment, researchers control the treatment (e.g., assigning some participants to a drug and others to a placebo).
• The third option is partially visible but likely incorrect as both can test cause - effect (experiments are better at it, but observational studies can also infer).
• The fourth option is incorrect as the time period is not a defining difference between the two.

Answer:

B. in an observational study, the researchers do not control treatment, and in an experiment, they do.