Fifty patients with heart arrhythmias are divided into two groups. One group receives
a new drug to regulate heart rhythm comma the other a placebo. After one month comma the presence of arrhythmias is measured.
Does the description correspond to an observational study or an experiment?
A.
The study is an observational study because the researchers control one variable to determine the effect on the response variable.
B.
The study is an observational study
because the study examines individuals in a sample comma
but does not try to influence the response variable.
C.
The study is an experiment
because the researchers control one variable to determine
the effect on the response variable.
D.
The study is an experiment because the study examines individuals in a sample, but does not try to influence the variable of interest.