Question 813311
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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= .8  & q = .2
nCx = {{{n!/(x!(n-x)!)}}}
P(2 out of 4) = {{{(4!/2!2!)(.8)^2(.2)^2}}} = .1536