Question

Verify the following function, which can be regarded as p.m.f. for the given values of X : 

X = x	-1	0	1
P(x)	-0.2	1	0.2

Answer 1

 In order that given function is p.m.f. it must satisfy

(i) P (X = x) ≥ ∀x and 

(ii) ΣP(X = x) = 1

In the given data P(-1) = - 0.2 < 0
Here P(X = x)  ≥ 0 , ∀x is not satisfied 
∴ Given function can not be regarded as p.mf.