1. 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 first group of 310 taking vitamin C alone
the second group of 418 taking 200 IU of vitamin E
the 1132 subjects
the third group of 404 taking 400 IU of vitamin E
There is no control group.
This study is
not blind.
double-blind
not an experiment
blind, but not double-blind
none of the above
2. To test the effectiveness of a liquid supplement that is
supposed to help forgetful people with their memory, 400 college
students are recruited for a study and divided into two groups.
Group A with 250 students receives the supplement, while group B
with 150 students receives some colored water. Neither group is
told what they received. After several weeks, they are given a
memory test. This study can best be described as
a survey using simple random sampling
a controlled placebo experiment
a census
the placebo effect
a survey using quota sampling