In: Statistics and Probability
The probability that one has been to Antarctica given that one is a traveler is .05. The probability that one has not been to Antarctica given that one is not a traveler is .999. The probability that one is a traveler is .10.
a/ What is the probability of having been to Antarctica?
b/ What is the probability of not being a traveler, given that you have been to Antarctica?
Let,
A: event that one has been to Antarctica.
T: event that one is a traveler.
We have given,
Probability that one is a traveler, P(T) = 0.10
Probability that one has been to Antarctica given that one is a traveler, P(A | T) = 0.05
Probability that one has not been to Antarctica given that one is not a traveler, P(Ac| Tc) = 0.999
So,
Probability that one has been to Antarctica given that one is not a traveler, P(A | Tc) = 1- 0.999 = 0.001
Probability that one is not a traveler, P(Tc) = 1- 0.10 = 0.90
Now,
a) The probability of having been to Antarctica = P(A | T) + P(A | Tc)
= 0.05 +0.001
= 0.051
b) The probability of not being a traveler, given that you have been to Antarctica i.e. P(Tc| A)
Using bayes theorem, we have