Question

you take 2 balls without replacement from the bag, 2 yellow and 7 pink find the expectation and the standard deviation of how many yellow balls you will get

Answer 1

The probability of getting a yellow ball on the first pick = 2/9. Without replacement, the probability of getting the second yellow ball = 1/8.

To find the probability of both or all events occurring, multiply the probabilities of the individual events.

I don't know how to get the last part (standard deviation).