oops wrote:

This is a repost of a Challenge question (Challenge 3, Q 26) posted several weeks back for which I have no response so far.

Store with 10 bottles of alcohol, of which 7 whiskeys.

If 6 bottles are sold, what is the prob of selling 4 whiskeys among the 6?

Given solution:

(7C4)(3C2)/(10C6) = 1/2

It seems to me that this solution assumes that 4 and only 4 whiskeys are sold. But the question doesn't exactly say that. The way the question is worded, it doesn't specify that the other 2 bottles that are sold are not whiskeys. Hence, it seems to me that we should calculate probability that atleast 4 whiskeys are sold. This gives (7C4)(6C2)/(10C6) = 5/8 as the answer (bcoz there are 6 (not 3) choices from which to pick the remaining two). Is this correct? If not, how to solve?

I am not a probability guru and would appreciate the opinion of a subject expert - since I am a little confused by this question/answer and am not sure if am on the right track.,. thanks!

Probability questions are very specific on at least, at most etc. Question specifies that 4 whiskey bottles were sold. since there is no at least I would go with the given explanation. My 2 cents. (Btw, I took probability in both undergrad and grad school so I can say that i have seen reasonably good number of P questions)

hth.