Probability of two people being born on the same day of the week - Cross Validated most recent 30 from stats.stackexchange.com 2019-10-22T01:16:03Z https://stats.stackexchange.com/feeds/question/388853 https://creativecommons.org/licenses/by-sa/4.0/rdf https://stats.stackexchange.com/q/388853 0 Probability of two people being born on the same day of the week user233991 https://stats.stackexchange.com/users/233991 2019-01-24T03:09:25Z 2019-01-24T03:20:26Z <p>What is the probability of two people being born on the same day of the week?</p> <p>I understand both of them individually have probability of 1/7 to be born on a certain day and that the two probabilities are independent of one another. So the answer could be 1/49. But that's a wrong answer.</p> https://stats.stackexchange.com/questions/388853/-/388854#388854 2 Answer by Siong Thye Goh for Probability of two people being born on the same day of the week Siong Thye Goh https://stats.stackexchange.com/users/128610 2019-01-24T03:20:26Z 2019-01-24T03:20:26Z <p>You still have to sum up the days.</p> <p>Let <span class="math-container">$A$</span> be the day that the first person is born on and <span class="math-container">$B$</span> be the day for the second person. </p> <p><span class="math-container">\begin{align} Pr(A=B) = \sum_{i=1}^7 Pr(A=i)Pr(B=i)=\frac17 \end{align}</span></p>