Elementary statistics
posted by Rose Bud on .
Nine apples, four of which are rotten, are in a refrigerator. Three apples are randomly selected without replacement. Let the random variable x represent the number chosen that are rotten. Construct a table describing the probability distribution, then find the mean and standard deviation for the random variable x.
question: WHAT STEPS WERE USED TO GET THE ANSWER?
this is the table
X P(x)
0 0.167
1 0.500
2 0.300
3 0.033

The total number of outcomes is 9C3, because there are nine apples and you are choosing 3 where order doesn't matter.
P(0) = 5C3 / 9C3
because there are 5 good apples and you need to choose 3.
P(1) = 5C2*4C1 / 9C3
P(2) = 5C1*4C2 / 9C3
P(3) = 5C0*4C3 / 9C3 
THANK YOU SO MUCH I have been stumped on this question for hours on two different occasions, I am so glad you cleared this up for me.