.
Among a group of 18 stocks, suppose that 9 will perform above average 
and the other 9 will perform below average. 
If you pick 4 stocks from this group, what is the probability 
that all 4 will be above average in performance?
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This problem is a TWIN to the problem solved 5 minutes ago under this link
https://www.algebra.com/algebra/homework/Probability-and-statistics/Probability-and-statistics.faq.question.1204025.html
The solution follows to the same logic.
    P =  =  =  = 0.041176  (rounded).    ANSWER
Solved.
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To see many other similar  (and different)  problems solved,  look into the lesson
    - Elementary Probability problems related to combinations 
in this site.
Learn the subject from there.