Statistics help PLEASE!!!?

Question

X } -18 -13 1 11 13
P(X) } 3/10 1/5 1/10 3/10 _?__

(THis is supposed to be a chart where you have to fill in)

THe directions are:
Given the following sampling distribution:(above)
What is the mean of this sampling distribution?
(Please show every step when completing this problem)

Answer 1

In order for the probabilities to sum to 1, P(13) must equal 1/10:
. X , P , XP
-18 0.3 -5.4
-13 0.2 -2.6
. 1 0.1 . 0.1
11 0.3 . 1.1
13 0.1 . 1.3
----- ----- -----
. . . 1.0 -5.7
X(mean) = - 5.7/1.0 = - 5.7