Add up the sum of the products of the sum and the probability of that sum.
Possible sums are 3,4,5,6,7,8 and 9.
There are 2 ways to get 3 or 9:
(1,2)(2,1); (4,5), (5,4)
There are 2 ways to get 4 or 8
There are 4 ways to get 5 or 7:
(1,4)(4,1)(2,3)(3,2); (2,5)(5,2);(4,3)(3,4)
There are 4 ways to get 6:
(1,5)(5,1)(2,4)(4,2)
The probability of getting 3,4,8 or 9 is 1/10. The probability of getting 5,6 or 7 is 1/5.
E = (1/10)(3+4+8+9) + (1/5)(5+6+7)
= 2.4 + 3.6 = 6
Five chips numbered 1-5 are placed in a jar. Two chips are drawn.
Let Z= the sum of the numbers.
WHat is the expected value of the random variable?
I know I have to use E = np
Can someone explain?
1 answer
1 answer