Browsing as Guest. Progress, bookmarks and attempts are disabled.
Log in to track your work.
June 2013 p61 q2
3321
Assume that, for a randomly chosen person, their next birthday is equally likely to occur on any day of the week, independently of any other person's birthday. Find the probability that, out of 350 randomly chosen people, at least 47 will have their next birthday on a Monday.
Solution
Let the random variable \(X\) represent the number of people whose birthday falls on a Monday. Since each day of the week is equally likely, the probability \(p\) that a person's birthday is on a Monday is \(\frac{1}{7}\).
We have \(n = 350\) people, so the expected number of people with a birthday on Monday is \(np = 350 \times \frac{1}{7} = 50\).
The variance is \(npq = 350 \times \frac{1}{7} \times \frac{6}{7} = 42.857\).
We use a normal approximation to the binomial distribution. Applying continuity correction, we find: