SOLUTION: Please help me solve probability question. The random variable X has the following distribution. x = -1, 9, 1, 2 P(X=x) 3c, 2c, 0.4, 0.1 What is the average?

Question 1081926: Please help me solve probability question.
The random variable X has the following distribution.
x = -1, 9, 1, 2
P(X=x) 3c, 2c, 0.4, 0.1
What is the average?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
E(X)=x*p(x)=-3c+18c+0.4+0.2=15c+0.6
However, we can solve for c initially
We know that the probability distribution has 0.5 accounted for, so 3c+2c=0.5
therefore, 5c=0.5
c=0.1
x=-1 with probability 0.3 and product -0.3
x=9 with probability 0.2 and product 1.8
x=1 with probability 0.4 and product 0.4
x=2 with probability 0.1 and product 0.2
E(X) is the sum or 2.1
This fits with c=0.1 above, since 15c+0.6=2.1
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