In order to have a successful study, there have to be two elements: an experimental group and a control group.  The experimental group is introduced to whatever is being tested – a new drug, for example – while the other group is given a placebo.  The two groups should be similar in composition and be consistent in all factors other than what’s being tested.

So read carefully to ensure that there hasn’t been a blanket application of the item being studied, or that other factors weren't consistent. If a new drug is introduced, but the experimental group is also getting supplements, researchers won’t be able to tell if the drug or the supplements were what caused the outcome.