Question 622065
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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 = .70 & q = .30  and n = 15
nCx = {{{n!/(x!(n-x)!)}}}
 P(x = 6) = 21C6(.7)^6(.3)^9 = 5005(.7)^6(.3)^9 = .012
 P(x &#8804; 6) =  P(0) + P(1) + P(2) + P(3) + P(4) + P(5) +  P(6) 
         = (.7)^0(.3)^15 + 2(.7)^1(.3)^14 + 105(.7)^2(.3)^13 + 455(.7)^3(.3)^12 + 1365(.7)^4(.3)^11 + 3003(.7)^5(.3)^10+ 5005(.7)^6(.3)^9
 (c) = {{{mu = 15*.70 = 10.5}}} and  
{{{sigma  =sqrt(15*.7*.3)= 1.7748}}}
  z = {{{(x-mu)/sigma}}}