Originally Posted by
MadisonDuBerlais Hello forum,
My names Frank and I've just signed up! I am currently struggling with my Probability especially Bayes theorem.
My first question is to find out what the probability of a letter that does not arrive the next day is 2nd class. The data I have available too me is;
1. 70% of Mail carries 1st class stamp.
2. 90% of 1st class mail arrives at its destination the next day.
Using Bayes Theorem
P(Letter Does Not Arrive/2nd Class) = 0.10 * 0.30
/
P(Letter Arives * 1st Class) + P(Letter does not arrive * 1st Class) = 0.72
ANS = 0.03/0.72 = 0.041
I know the ANS is 0.632 but I just don't know how to get there!