Question

a study claims that the combination of vitamin c with vitamin e is more effective for preventing the flu than vitamin c alone. in the study, a group of researchers studied 1132 subjects. the subjects were randomly assigned to out of three study groups. the first group of 310 subjects were instructed to take 600 mg daily of vitamin c. the second group of 418 subjects were instructed to take 600 mg of vitamin c and 200 iu of vitamin e daily. the third group of 404 subjects were instructed to take 600 mg of vitamin c and 400 iu of vitamin e daily. the incidence of flu over a season was recorded. all subjects knew which treatment they were receiving.

in this study, which is the control group?
the 1132 subjects
the third group of 404 taking 400 iu of vitamin e
the first group of 310 taking vitamin c alone
the second group of 418 taking 200 iu of vitamin e
there is no control group.

this study is
double-blind
blind, but not double-blind
not blind.
not an experiment
none of the above

Explanation:

🆕 New Concept Discovered: Experimental Design Elements
Identifying baselines and blinding in studies

Step 1: Identify the Control Group

A control group serves as a baseline for comparison, receiving either no treatment, a standard treatment, or a placebo.

The study's main claim is that the combination of vitamin C and vitamin E is more effective than vitamin C alone.

• Treatment Group 1: Vitamin C + 200 IU Vitamin E
• Treatment Group 2: Vitamin C + 400 IU Vitamin E
• Baseline/Comparison Group: Vitamin C alone (to see if adding Vitamin E makes a difference)

Therefore, the group of 310 subjects taking vitamin C alone serves as the control group.

Step 2: Determine the Blinding Status

Blinding refers to whether the subjects and/or researchers know which treatment is being administered:

• Single-blind: The subjects do not know which treatment they are receiving.
• Double-blind: Neither the subjects nor the researchers administering the treatments know who is receiving what.
• Not blind: The subjects know which treatment they are receiving.

The text explicitly states: "All subjects knew which treatment they were receiving." Therefore, this study is not blind.

Answer:

• In this study, which is the control group?

the first group of 310 taking vitamin C alone

• This study is

not blind.