Statistics problem.

A quiz cosists of 10 multiple-choice questions, each with 4 possible answers. For someone who makes random guesses for all of the answers, find the probability of passing if the minimum passing grade is 60 %.

n = 10, p = 1/4, 60% of 10 = 6, so x >=6

P(6 <= x <= 10) = 0.0197277 <------ (That's the answer) I just don't know how they got this answer.

 

Alright, always start with the percent required to pass and the number of questions. 60% of 10 is 6 questions, so we need +6 and -4.

Then just throw all of that gathered information into your standard equation.

P(pass) = ((n)c6)(p)^6*(p)^4

Simplify further..

P(pass) = (10c6)(1/4)^6*(1/4)^4

Calculate that and you have your answer.