0 votes 0 votes closed as a duplicate of: 19. a) What is the probability that two people chosen at random were born during the same month of the year? what is the probability that in a group of n people chosen at random, there are atleast two people born in the same month of the year? Probability kenneth-rosen probability + – aditi19 asked Dec 1, 2018 closed Dec 1, 2018 by Mk Utkarsh aditi19 465 views comment Share Follow See all 7 Comments See all 7 7 Comments reply Show 4 previous comments kumar.dilip commented Dec 1, 2018 reply Follow Share aditi19 P(X') = 12 * 11 * .. (12-n+1) / $12^{n}$ (As the first person has 12 months to choose from, second person has 11, an when n = 13 then 12 - 13 + 1 = 0 ( here person birth choice is zero , it will be one of the 12 month which already choosen) when n > 12 , then pigeonhole principle will work here. 0 votes 0 votes aditi19 commented Dec 1, 2018 reply Follow Share but when n=14, 12-n+1=12-14+1=-2+1=-1. what does this indicates? 0 votes 0 votes kumar.dilip commented Dec 1, 2018 reply Follow Share It means two people birthmonth will not be unique, it will be repeated between the month 1 and 12. 0 votes 0 votes Please log in or register to add a comment.