Consider the two-way table below.
\begin{tabular}{|c|c|c|c|}
\cline { 2 - 4 } & C & D & Total \\
\hline A & 15 & 21 & 36 \\
\hline B & 9 & 25 & 34 \\
\hline Total & 24 & 46 & 70 \\
\hline
\end{tabular}

Find [tex]$P(B \mid C )$[/tex].

A. [tex]$P(B \mid C )=\frac{9}{34}=0.26$[/tex]

B. [tex][tex]$P(B \mid C )=\frac{9}{24}=0.38$[/tex][/tex]

C. [tex]$P(B \mid C )=\frac{9}{70}=0.13$[/tex]

D. [tex]$P(B \mid C )=\frac{9}{58}=0.16$[/tex]



Answer :

To find the conditional probability [tex]\( P(B \mid C) \)[/tex], we need to determine the probability that event B occurs given that event C has already occurred.

Here is a step-by-step breakdown of how to solve for [tex]\( P(B \mid C) \)[/tex]:

1. Identify the relevant events from the table:
- Event B: characterized by row 'B' in the table.
- Event C: characterized by column 'C' in the table.

2. Find the value of [tex]\( P(B \cap C) \)[/tex]:
- This is the number of times both B and C occur together. Looking at the table, we can see that the count for both B and C is 9.

3. Find the total number of occurrences of event C:
- This is given in the total column under C, which is 24.

4. Calculate the conditional probability [tex]\( P(B \mid C) \)[/tex] using the formula:
[tex]\[ P(B \mid C) = \frac{P(B \cap C)}{P(C)} \][/tex]
Substituting the values we found:
[tex]\[ P(B \mid C) = \frac{9}{24} \][/tex]

5. Simplify the fraction and convert to a decimal:
[tex]\[ \frac{9}{24} = \frac{3}{8} \approx 0.375 \][/tex]

6. Round the result to two decimal places:
[tex]\[ P(B \mid C) \approx 0.38 \][/tex]

So, the conditional probability [tex]\( P(B \mid C) \)[/tex] is indeed [tex]\( \frac{9}{24} = 0.38 \)[/tex].

Thus, the correct answer is:
[tex]\[ P(B \mid C) = \frac{9}{24} = 0.38 \][/tex]