If the probability distribution table for no, of "Heads'' in three throws of coin is  X 0 1 2 3 P(X=x) 1/8 3/8 3/8 1/8 Then Var (X) is:

3/4 3/8 3/16 3/32

3/4

xi   Pi     Pixi Pixi2 0 1/8 0 0 1 3/8 3/8 3/8 2 3/8 6/8 12/8 3 1/8 3/8 9/8     $∑Pixi=\frac{12}{8}=\frac{3}{2}$ $∑Pixi^2=\frac{24}{8}=3$   $Var(X)=∑P_ix_i^2-(∑P_ix_i)^2 = 3-(\frac {3}{2})^2=\frac{3}{1}-\frac {9}{4}=\frac {12-9}{4}=\frac{3}{4}$