In clinical trials the tests are usually carried out in two groups. The first group
is given the new drug and the second group is either given the old drug or a
placebo. The placebo is a something that looks like a drug but is not. They
are split into two groups to ensure that they can compare the results.
Sometimes these trials are carried out in different ways. Blind trials – these
are trials where the volunteers do not know whether they are receiving the
drug or not.
Double bind trials – these trials are when both the volunteers and the
scientist do not know who is receiving the drug or the place.