Question

Joe’s friend is an avid surfer who goes to a certain surfing location every year, stays there until he has had 5 good surfing days and then leaves. At that location, the probability that a day is good according to Joe’s friend’s standards is estimated to be equal 0.6 independently of other days. Joe came to the same location one week (7 days) later than his friend who was still there. Given only this information, what is the probability that Joe’s friend will stay for at least one more week?

Answer 1

Let X=no. of days that the Joe's friend stays there until he has had 5 good surfing days

then X follows Negative Binomial(5, 0.6).

Use R code:

round((1-pnbinom(13-5,5,0.6))/(1-pnbinom(6-5,5,0.6)),4)