Clinical trials: Medical experiments designed to assess which of two or more treatments is much more effective. It is based on one of the oldest philosophy of the scienti?c research, namely that the new information is attained from the comparison of the alternative states. The three main components of a clinical trial are given below:

* Comparison of the group or set of patients given the treatment under the investigation with another group or set of the patients given either an older or the standard treatment, in one exists, or an 'inert treatment' commonly known as the placebo (or the control group).

Some trials might include more than two groups.

* A way of assigning patients to the treatment and control groups or sets.

* A measure of the outcome, that is a response variable.

One of the most significant aspects of the clinical trial is the question of how the patients should be allocated to the treatment and the control group. The objective in the allocation is that the treatment group and control group should be similar in all respects except treatment taken. As a result the clinical trial is more likely to give an unbiased estimate of the difference between the two treatments. The most suitable (perhaps only suitable) method of the allocation is randomization leading to randomized clinical trials, the gold standard for the treatment assessment.