[robochat]

Can anyone explain the maths that he did because my calculation give different results. Isn't there only a 1 in 2588 chance of a student 'guessing' 19 'answers' out of 45 where there are 5 options for each answer? Whereas the article states that it is 1 in 100 ? (actually he writes 1:100 which is odds, so it is 1 in 101?) Don't we just use the Binomial distribution, so: Prob = 45!/(19!26!) * (1/5)*19 * (1 - 1/5)*26 It's really bugging me that I can't get the maths to work.