Question 519:

Asked on November 23, 2008

Tags: Probability , Random Variable , Compliment Rule

1

Answer:

No answer provided yet.

For a discrete random variable, which this is, the total probability of all values should add up to 1. So you're given two unknown values. If you had just 1 unknown you could figure out the missing value by adding up all the others, then subtract this from 1. You have 2 unknowns so we can't do this. With no other information, it is impossible to answer this question. The only answer I can come up with is:

Value x of X                      P (X=x)
-4                                     0.13
1                                      0.15
2                                      0.52-x
3                                      0.20
6                                        x

I'm using .52 because the known values sum to .48 making the other two values having to sum to .52 to make them both 1(called the complement rule of probability).  But these two values could take on any combination of values which would add up to .52 (e.g. .26 and .26, .51, .01 etc).