Question

In a class of students, the following data table summarizes how many students have a cat or a dog. What is the probability that a student who does not have a dog has a cat?
Has a cat Does not have a cat
Has a dog 8 3
Does not have a dog 9 7

Answer 1

We want P(cat | not dog) = (number with cat and no dog) / (total number with no dog).

Number with no dog = 9 + 7 = 16, and of those 9 have a cat. So the probability is 9/16 = 0.5625 = 56.25%.