A hint to get started
Translate birthday counts and find a strict minimum sample size
It may be assumed that the dates of birth in a large population are distributed throughout the year so that the probability of a randomly chosen person’s date of birth being in any particular month may be taken as .
(i) Find the probability that, of 6 people chosen at random, exactly 2 will have birthdays in January. marks
(ii) Find the probability that, of 8 people chosen at random, at least one will have a birthday in January. marks
(iii) people are chosen at random. Find the least value of such that the probability that at least one will have a birthday in January exceeds 0.9. marks
(iv) Find the probability that, of 100 people chosen at random, at least 40 will have birthdays in May, June, July or Agusut. marks
[J84/I/12]
CJC · Review Problems · Question 9
Use the complement for at least one and reverse the inequality when dividing by a negative logarithm.