In any discrete series, the relationship between mean deviation from mean (M.D) and standard deviation (S.D) is
M.D = S.D
M.D > S.D
M.D < S.D
M.D≤S.D
S.D=√1N∑fi(xi−¯x)2andM.D=1N∑fi|xi−¯x|let|xi−¯x|=yi
S.D2−M.D2=1N∑fiy2i−(1N∑fiyi)2=σ2(y)≥0∴S.D≥M.D
Standard deviation about mean (¯x) for a given discrete frequency distribution x1,x2,x3,.....xn with frequencies f1,f2,f3,...fn is
Standard deviation about mean ¯x for a given discrete frequency distribution x1, x2, x3, ....xn with frequencies f1, f2, f3, .... fn is.