A random variable has aprobability function p(x)=kx; x=1,2,3,4,5.find the value of k, p(x>=3),compute mean and variance of x.

Answer 1

k(1+2+3+4+5) = 1
k = 1/15

p(3) = 3/15
p(4) = 4/15
p(5) = 5/15

so p (x>/=3) = 12/15 = 4/5
etc