Standard deviation of a Distribution The distribution's standard deviation is the square root of its variance; 2 st dev[w]=ow=voi ∑(s-1)2xs St deviation also measures thervs variabilityStandard Deviation of a Distribution The distribution’s standard deviation is the square root of its variance; St. deviation also measures the r.v.’s variability. st. dev[w] w w (w ) . s w s s S = = = − =      2 2 1