The purpose of experimental pharmacology is to always look for any drug that can produce a statistically significant difference in physiology of living system. In an easy to understand language, a pharmacologist or student of pharmacology is always looking for any drug treatment that is beneficial to human physiology. Such useful drug treatment may be helpful to humans in three main ways: (a) It can help to
improve the functions of our body organ/tissue/cell; (b) it can help cure a disease or any discomfort in
our body, and/or (c) it can help to diagnose a disease or any discomfort in our body. Before making any
positive comment on usefulness of any drug treatment, a pharmacologist needs to test this treatment on
living body. The useful activity of treatment is called as Desired Effect or Desired Activity. The basic
need is that the pharmacologist must clearly know the site in body (organ or tissue/cell), where the
desired activity is required. After the site of desired effect is clear, it is necessary to bring this treatment
in contact with site of desired effect. After this, a pharmacologist or student always wishes to observe
the difference, produced by treatment in living body. In case of preclinical pharmacology, this living
body may be of any “animal”. Whether a significant difference is produced or not in animal, a comparison
is made between animal, treated with treatment and untreated animal. After this, a suitable test of
statistical analysis is selected to compare the observations (data) collected from treated animal and
untreated animal.