Question

Let X be a random variable defining number of students getting A grade. Find the expected value of X from the given table.

X = x	0	1	2	3
P (X = x)	0.2	0.1	0.4	0.3

Answer 1

Expected value of X, E(X) = ∑_xxP_x(x)

E(X) = (0 × 0.2) + (1 × 0.1) + (2 × 0.4) + (3 × 0.3) 

= 0 + 0. 1 + 0.8 + 0.9 

= 1.8