Answer:
0.0157
Step-by-step explanation:
From the information given:
The sample size = 70
The expected no. of days of year that are birthday of exactly 4 people is:[tex]P = \bigg [ \dfrac{1}{365} \bigg]^4[/tex]
The expected number of days with 4 birthdays = [tex]\sum \limits ^{365}_{i=1} E(x_i)[/tex]
[tex]\sum \limits ^{365}_{i=1} E(x_i) = 365 \times \bigg[ \ ^{70}C_{4} \times ( \dfrac{1}{365})^4 ( 1 - \dfrac{1}{365})^{70-4} \bigg][/tex]
[tex]\sum \limits ^{365}_{i=1} E(x_i) = 365 \times \bigg[ \ \dfrac{70!}{4!(70-4)!} \times ( \dfrac{1}{365})^4 ( 1 - \dfrac{1}{365})^{66} \bigg][/tex]
[tex]\sum \limits ^{365}_{i=1} E(x_i) = 365 \times \bigg[ \ 916895 \times 5.6342 \times 10^{-11} \times 0.8343768898 \bigg][/tex]
= 0.0157
Therefore, the required probability = 0.0157
