Question

which example describes the set-up of a controlled experiment?
ten subjects receive a new drug and another ten subjects receive a sugar pill.
researchers collect lifestyle data from fifty questionnaires submitted by subjects with the same disease.
fifteen subjects with the common cold take a cold medicine and answer questions about its effects.
a doctor treats one subject for a disease and observes how quickly the patient recovers.
twenty subjects with knee pain receive the same treatment to relieve joint pain.

Explanation:

A controlled experiment has an experimental group (receiving the treatment) and a control group (receiving a placebo or no treatment to compare). In the first option, ten subjects get the new drug (experimental group) and ten get a sugar pill (control group), which fits a controlled experiment setup. The other options either lack a control group (collecting lifestyle data, subjects taking medicine without a control, single - subject treatment, same treatment for all) or are observational/non - controlled.

Answer:

A. Ten subjects receive a new drug and another ten subjects receive a sugar pill.