<prompt> Most common deviation used in social medicine is-MeanRangeVarianceStandarddeviation  <response>: Ans. is d i.e.. Standard deviation Standard deviation is most common and generally most appropriate measure of dispersion variation -Park Standard deviation SD1o Standard deviation is a measure of dispersion variation,o It is a measure of spread dispersion of data about the mean.o In simple terms, it is defined as Root - means - square - deviationo It is denoted by letter sigma s.o When the sample size is more than 30, the above basic formula may be used without modification. For smaller samples, the above above formula tends to underestimate the standard deviation, and therefore needs correction, which is done by substituting the denominator r - 1 for T. 