Question

Find the mean and standard deviation of the distribution shown. x 4 2 1 0 P(x) 0.27 0.14 0.54 0.05

Answer 1

X	P(X)	X*P(X)	X² * P(X)
4	0.270	1.08	4.320
2	0.140	0.28	0.560
1	0.540	0.54	0.5400
0	0.050	0	0.0000

mean = E[X] = Σx*P(X) =            1.90000
          
E [ X² ] = ΣX² * P(X) =            5.4200
          
variance = E[ X² ] - (E[ X ])² =            1.8100
          
std dev = √(variance) =            1.3454