Question

Verify whether the following function can be regarded as probability mass function (p.m.f.) for the given values of X : 

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

Answer 1

Here P(X = -1) = - 0.2 

i.e. P(X = x) < 0, for x = -1 

∴ The function is not a p.m.f.