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 didn’t, 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. Let's analyze each option:

• Option A: This is not an experimental design with treatment (drug) administration, so it's not a double - blind experiment.
• Option B: If only the patients know who is getting which drug, the researchers know, so it's not double - blind (it's single - blind from the researcher's perspective, but not double - blind).
• Option C: If neither the patients nor the researchers know who is getting the drug or the placebo until the study is concluded, this fits the definition of a double - blind experimental design.
• Option D: This is an observational study, not an experimental design with treatment, so it's not a double - blind experiment.
• Option E: This is a statistical analysis of existing data, not an experimental design, so it's not a double - blind experiment.

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