Chance It is a common practice to judge a result significant, if it is of such a magnitude that it would have been produced by chance not more frequently than…

Prevention If a patient asks a medical practitioner for help, the doctor does the best he can. He is not responsible for defects in medical knowledge. If, however, the practitioner…

Treatment Treatments should be given “not because they ought to work, but because they do work.” —L.H. Opie 1980 KEY WORDS Hypotheses Treatment Intervention Comparative effectiveness Experimental studies Clinical trials…

Diagnosis Appearances to the mind are of four kinds. Things either are what they appear to be; or they neither are, nor appear to be; or they are, and do…

Prognosis He, who would rightly distinguish those that will survive or die, as well as those that will be subject to disease a longer or shorter time, ought, from his…

Risk: From Disease to Exposure “… take two groups presumed to be representative of persons who do and do not have the disease and determine the percentage of each group…

Risk: Exposure to Disease From the study of the characteristics of persons who later develop coronary heart disease (CHD) and comparison with the characteristics of those who remain free of…

Risk: Basic Principles The lesson … is that a large number of people at a small risk may give rise to more cases of disease than the small number who…

Abnormality … the medical meaning of “normal” has been lost in the shuffle of statistics. —Alvan Feinstein 1977 KEY WORDS Nominal data Dichotomous data Ordinal data Interval data Continuous data…

Frequency Here, it is necessary to count. —P.C.A. Louis† 1787-1872* KEY WORDS Numerator Denominator Prevalence Point prevalence Period prevalence Incidence Duration of disease Case fatality rate Survival rate Complication rate…