My question is based on Sheldon M Ross' 'First Course in Probability'
Fifty-two percent of the students at a certain college are females. Five percent of the students in this college are majoring in computer science. Two percent of the students are women majoring in computer science. If a student is selected at random, find the conditional probability that
- the student is female given that the student is majoring in computer science;
- this student is majoring in computer science given that the student is female.
My Approach:
Let F = Random selected student is a female, so $P(A) = 0.52$
C = Random selected student is majoring in Computer Science, so $P(C) = 0.05$
and Probability that 2% women are majoring in computer science is equivalent to probaility of random selected student is doing computer science given she's a woman. Therefore, $P(F|C) = 0.02$
End
I am aware that the above conditional approach is wrong. But why is it so? According to a solution I found over the internet, it should be $P(F \cap C) = 0.02$.
But why? I want to understand the intution behind this and approach questions more of this type.
Thanks!
You are told in the question
You are misinterpreting this statement to be a follow-up to the previous sentence; i.e., you are thinking that it means
But the sentences are separate because if the author had meant the second (conditional) interpretation, he would have written it that way.
So $\Pr[F \cap C] = 0.02$.
Furthermore, the first part of the question would be trivially answered under your interpretation.