Question 1199508
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n = 16 = number of questions
p = 1/4 = 0.25 = probability of success on any question
x = 4 = number of desired successes


Use the binomial probability formula
B(x) = (n C x)*p^x*(1-p)^(n-x)
B(4) = (16 C 4)*0.25^4*(1-0.25)^(16-4)
B(4) = (1820)*0.25^4*(1-0.25)^(16-4)
B(4) = 0.22519906517119
B(4) = 0.225199


There's about a 22.5199% chance of getting exactly four correct answers.


The nCx notation refers to the nCr combination formula.
{{{nCr = (n!)/(r!*(n-r)!)}}}
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