In a multiple choice test an examinee either knows the correct answer with probability p or guesses ......

In a multiple-choice test, an examinee either knows the correct answer with probability p, or guesses with probability 1- p. The probability of answering a question correctly is 1 / m , if he or she merely guesses. If the examinee answers a question correctly, the probability that he or she really knows the answer is -

P(he/she know correct answer) = p

P(he/she guess correct answer) = (1-p)×1 / m 

P(correct answer) = p + 1−p / m 

P(he/she really know correct answer)

= p / p+ 1− p / m

= mp / 1+p(m−1)

By: Yachna