Ex 13.3, 4 - Chapter 13 Class 12 Probability (Term 2)
Last updated at Feb. 15, 2020 by Teachoo
Bayes theorem
Ex 13.3, 2 Important
Ex 13.3, 3
Misc 3
Ex 13.3, 4 Important You are here
Ex 13.3, 9
Ex 13.3, 5
Ex 13.3, 13 (MCQ) Important
Example 21 Important
Ex 13.3, 6 Important
Ex 13.3, 10 Important
Example 18 Important
Example 17 Important
Ex 13.3, 7
Ex 13.3, 8 Important
Example 19 Important
Ex 13.3, 11
Ex 13.3, 12 Important
Example 37 Important
Example 20 Important
Example 33 Important
Misc 12
Misc 16 Important
Misc 13 Important
Bayes theorem
Ex 13.3, 4 In answering a question on a multiple choice test, a student either knows the answer or guesses. Let 3/4 be the probability that he knows the answer and 1/4 be the probability that he guesses. Assuming that a student who guesses at the answer will be correct with probability 1/4. What is the probability that the student knows the answer given that he answered it correctly?Let A : student know the answer B : student guesses C : student answers correctly We need to find the Probability that the student knows the answer, if he answered it correctly i.e. P(A|C) P(A|C) = ("P(A)" ." P(C|A)" )/" P(A) . P(C|A) + P(B) P(C|B) " "P(A)" = Probability that student knows the answer = π/π "P(C|A)" = Probability that the student correctly, if he knows the answer = 1 "P(B)" = Probability that the student guesses the answer = π/π "P(C|B)" = Probability that the student correctly, if he guesses = π/π Putting values in formula, P(A|C) = (3/4 Γ 1)/( 1/4 Γ 1/4 + 3/4 Γ 1 ) = (1/4 Γ 3)/( 1/4 [ 1/4 + 3 ] ) = 3/( 1/4 + 3 ) = 3/( 13/4 ) = 12/13 Therefore, required probability is ππ/ππ