A graduate student who takes 3 courses in one semester If Xt

A graduate student who takes 3 courses in one semester. If X=the number of courses with grade “A”. The random variable X has a probability distribution as follows

x

0

1

2

3

p(x)

0.2

0.1

0.6

0.1

The probability P(X <3) is equal to

Solution

P(X<3)

=P(X=0)+P(X=1)+P(X=2)

=0.2+0.1+0.6

=0.9