MATH 251, Prob & Stat I, help on algebra of means/ variances problems

Distributions for C:
y\\x 0    4    10    10   w = x + y, in table body
4   *4   *8   *14   *14
2   *2   *6   *12   *12
1   *1   *5   *11   *11
1   *1   *5   *11   *11

W 1, 2, 4, 5, 6, 8, 11, 12, 14

p 2  1  1  2  1  1   4   2   2  (number of times the W-value occurs)
Divide all p-values by 16, to get the probability.

and D:  

y\\x 0    4   10   10  z = x - y
4  *-4   *0   *6   *6
2  *-2   *2   *8   *8
1  *-1   *3   *9   *9
1  *-1   *3   *9   *9   

Z  -4, -2, -1, 0, 2, 3, 6, 8, 9

p   1   1   2  1  1  2  2  2  4 (number of times the Z-value occurs)
Divide all p-values by 16, to get the probability.

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10/18/05