Researchers conducted an experiment to identify the effects of three different hand sanitizers on the growth of bacteria. the
researchers grew one type of bacteria in twenty-four identical covered petri dishes. then, they opened eighteen petri dishes
and applied the three hand sanitizers to six petri dishes each. they left the remaining six petri dishes closed as a control
group. when the researchers measured the growth of bacteria two days later, the six dishes that had no hand sanitizer
showed the least amount of bacterial growth. the researchers concluded that not using any hand sanitizer would lead to the
least bacterial growth.
which statement best explains why the researchers' conclusion was not justified?
the experiment tested too many variables.
the control group was not treated the same as the experimental group.
the sample size of twenty-four petri dishes is not large enough.
the single type of bacteria is not adequate to make any conclusions.