SUBJECTIVE BIAS brings to mind the importance of the double-blind test, which is the only scientific device specifically developed for the clinical investigation of drugs. Its principle is a familiar one: During the research, neither the patient nor his physician knows whether the allegedlyactive drug, a placebo, or a known standard drug for comparison is being given. In that way, the physician's attitude can be isolated so it will neither influence his judgment, nor cause the patient's improvement to be ascribed to the drug when it is actually a nonpharmacological effect.
By excluding subjective bias, the double-blind test has made therapeutic research scientific. Few drugs can be confirmed to be of value without its use. However, the double-blind test eliminates subjective bias only from the data of a single experiment. If we assume that all subjective bias is eliminated, we overlook the factor which makes clinical pharmacology such a confused
Greiner T. Subjective Bias of the Clinical Pharmacologist. JAMA. 1962;181(2):120-121. doi:10.1001/jama.1962.03050280050005f