Question 436898
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Hi
Note: The probability of x successes in n trials is: 
P = nCx* {{{p^x*q^(n-x)}}} where p and q are the probabilities of success and failure respectively. 
In this case p = .25 and q = .75  and n = 7
nCx = {{{n!/(x!(n-x)!)}}}
P( sample contains 4 minorities) = 35(.25)^4(.75)^3
P(sample < than 2 minorities)= P(0)+P(1) =  (.75)^7 + 7(.25)(.75)^6
P(sample contains exactly 1 non-minority) = 7(.25)(.75)^6

expected value of minorities in the sample = .25*7 = 1.75