Question

read the following scenario.
after getting their results in, a group of scientists went back and looked at their study. as planned, their experiment consisted of three groups. the first group received a new medicine at a normal dose, the second group received the medicine at half the dose, and the third group received the medicine at twice the dose.
which of the following best describes what went wrong with the scientists study?
an improper experimental procedure
the lack of a control group
selection bias
human error

Explanation:

In a scientific experiment, a control group is a group that does not receive the treatment (in this case, the medicine) or receives a placebo. Here, all three groups received the medicine at different doses, and there is no group that serves as a baseline (control group) to compare the effects of the medicine against. An improper experimental procedure is too vague, selection bias relates to how participants are chosen (not the case here), and human error implies mistakes in execution (not indicated here). So the lack of a control group is the main issue.

Answer:

the lack of a control group