# Thread: expected value and standard dev

1. ## expected value and standard dev

In a box there are 25 marbles, 15 of which are red, 13 made of clay (only
6 of these are red). We randomly select 8 marbles without replacement.
If
U (V ) is the number of red (clay) marbles in our sample, find:

a) the expected value and standard deviation of 2U 3V + 4
b) Pr(3U = V )

2. ok im pretty sure i got b. but a is still in question

would it just be 2(15C8)/(25C8) - 3(13C8)/(25C8) + 4 for the expected value