Hi,

Note: The probability of x successes in n trials is: 

P = nCx where p and q are the probabilities of success and failure respectively. 

In this case, Yes!  p = .20 & q = .80

P(15 correct out of 20 questions)= 20C15 (.20)^15 (.80)^5 = 15,504(.20)^15 (.80)^5= .00000017

Probability so...small, UNLIKELY 

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