Conditional Probability
First, we must complete the totals in the table as follows:
The formula for the conditional probability is:
[tex]P(B|A)=\frac{P(B\cap A)}{P(A)}[/tex]Where A is an event we know has already occurred, B is an event we want to calculate its probability of occurrence, and P∩A is the probability of both occurring.
We know a female student has been selected, so that is our known event and:
[tex]P(A)=\frac{16}{30}=\frac{8}{15}[/tex]The probability that a female student is also a senior is:
[tex]P(A\cap B)=\frac{3}{30}=\frac{1}{10}[/tex]Substituting:
[tex]\begin{gathered} P(B|A)=\frac{\frac{1}{10}}{\frac{8}{15}} \\ \\ P(B\lvert\rvert A)=\frac{1}{10}\frac{15}{8}=\frac{3}{16} \end{gathered}[/tex]The required probability is 3/16
