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Below a two-way table is given for student activities:

[tex]\[
\begin{tabular}{|c|c|c|c|c|}
\hline
& Sports & Drama & Work & Total \\
\hline
Sophomore & 20 & 7 & 3 & 30 \\
\hline
Junior & 20 & 13 & 2 & 35 \\
\hline
Senior & 25 & 5 & 5 & 35 \\
\hline
Total & 65 & 25 & 10 & 100 \\
\hline
\end{tabular}
\][/tex]

Follow the steps to find the probability a student is in sports, given that they are a senior.

Use the formula below to get your final answer:

[tex]\[
\begin{array}{c}
P(\text{senior}) = 0.35 \quad P(\text{senior and sports}) = 0.25 \\
P(\text{sports} \mid \text{senior}) = \frac{P(\text{sports and senior})}{P(\text{senior})} = [?] \%
\end{array}
\][/tex]


Sagot :

To find the probability that a student is involved in sports given that they are a senior, we follow these steps:

1. Determine the given probabilities:

- Probability that a student is a senior: [tex]\( P(\text{senior}) \)[/tex]
- Probability that a student is a senior and involved in sports: [tex]\( P(\text{senior and sports}) \)[/tex]

From the provided table, we find:

- Total number of seniors: 35
- Number of seniors involved in sports: 25
- Total number of students: 100

2. Calculate the probabilities:

- [tex]\( P(\text{senior}) = \frac{\text{Number of seniors}}{\text{Total number of students}} = \frac{35}{100} = 0.35 \)[/tex]
- [tex]\( P(\text{senior and sports}) = \frac{\text{Number of seniors involved in sports}}{\text{Total number of students}} = \frac{25}{100} = 0.25 \)[/tex]

3. Find the conditional probability:

The probability that a student is involved in sports given that they are a senior is given by the formula:
[tex]\[ P(\text{sports} \mid \text{senior}) = \frac{P(\text{senior and sports})}{P(\text{senior})} \][/tex]

Plugging in the values we calculated:

[tex]\[ P(\text{sports} \mid \text{senior}) = \frac{0.25}{0.35} = 0.7142857142857143 \][/tex]

To convert this probability to a percentage:

[tex]\[ P(\text{sports} \mid \text{senior}) \times 100 = 0.7142857142857143 \times 100 = 71.42857142857143\% \][/tex]

So, the probability that a student is involved in sports given that they are a senior is approximately [tex]\( 71.43\% \)[/tex].