A<unk>  is a type of clinical study where two groups of treatments, A and B, are given so that one group receives only A while another group receives only B. Other names for this type of study include "between patient" and "non-crossover". This is unlike a crossover study where at first one group receives treatment A and later followed by treatment B while the other group receives treatment B followed by treatment A. There are, however, certain characteristics that allow for differentiation between these two types of trials. For example, a<unk>  would be more appropriate if any concerns about carryover effects were present. This type of study might also be more beneficial if the disease or disorder being studied has a likely chance of progression during the time in which the study takes place. One significant issue with<unk> es, though, is the concept of intra subject variability, which is defined as variability in response occurring within the same patient. The two treatment groups in a<unk>  can either consist of two completely separate treatments (i.e. different drugs), or simply different doses of a common drug. One major aspect of a<unk>  is randomization – this ensures that the results are accurate and have a lower risk of being biased. Control groups utilizing a placebo, or active control, are often used in this type of study.
Parallel study
Multiple baseline design
Intersalt study
Natural history study
Clinical study design
Blinded experiment
Confirmatory trial
Mixing study