Question

a researcher wishes to study the impact of a new drug on sleep length. which of the following would be an example of a double - blind experimental design?
a. if the researcher conducted the data through an intermediary company without administering any treatment or giving the drug
b. if the researcher divided the group into patients who received the placebo and those who received the drug, and only the patients knew who was getting each drug
c. if the researcher divided the group into patients who received the drug and those who didnt, and nobody knew if it was the drug or placebo until the study was concluded
d. if the researcher observed the patients without administering any treatment
e. if the researcher analyzed the sleep patterns of 100 patients and examined which factors were relevant through a stepwise regression

Explanation:

A double - blind experiment is one where neither the participants (patients) nor the researchers know who is receiving the treatment (drug) or the placebo until the study is completed.

• Option A: There is no treatment or drug administration, so it's not a double - blind experiment.
• Option B: Only the patients know, which is a single - blind (patient - blind) experiment, not double - blind.
• Option C: Neither the patients nor the researchers know who is getting the drug or placebo until the study ends, which fits the definition of a double - blind experimental design.
• Option D: This is an observational study without treatment, not an experimental design, let alone a double - blind one.
• Option E: This is a statistical analysis of existing data, not an experimental design.

Answer:

C. If the researcher divided the group into patients who received the drug and those who didn't, and nobody knew if it was the drug or placebo until the study was concluded