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A survey asks teachers and students whether they would like the new school mascot to be a pirate or a moose. This table shows the results.

\begin{tabular}{|l|c|c|c|}
\hline & Pirates & Moose & Total \\
\hline Students & 75 & 15 & 90 \\
\hline Teachers & 5 & 15 & 20 \\
\hline Total & 80 & 30 & 110 \\
\hline
\end{tabular}

A person is randomly selected from those surveyed. Are being a student and preferring "pirate" independent events? Why or why not?

A. Yes, they are independent because [tex][tex]$P(\text{student}) \approx 0.82$[/tex][/tex] and [tex][tex]$P(\text{student} \mid \text{pirate}) \approx 0.94$[/tex][/tex].

B. No, they are not independent because [tex][tex]$P(\text{student}) \approx 0.82$[/tex][/tex] and [tex][tex]$P(\text{student} \mid \text{pirate}) \approx 0.83$[/tex][/tex].

C. No, they are not independent because [tex][tex]$P(\text{student}) \approx 0.82$[/tex][/tex] and [tex][tex]$P(\text{student} \mid \text{pirate}) \approx 0.94$[/tex][/tex].


Sagot :

To determine whether being a student and preferring "pirate" are independent events, we need to compare the probability of a person being a student, [tex]\(P(\text{student})\)[/tex], with the conditional probability of a person being a student given that they prefer pirates, [tex]\(P(\text{student} \mid \text{pirate})\)[/tex].

### Step-by-Step Calculation:

1. Total number of people surveyed:
[tex]\[ 110 \][/tex]

2. Total number of students:
[tex]\[ 90 \][/tex]

3. Total number of people who prefer pirates:
[tex]\[ 80 \][/tex]

4. Number of students who prefer pirates:
[tex]\[ 75 \][/tex]

5. Probability of a person being a student:
[tex]\[ P(\text{student}) = \frac{\text{Total number of students}}{\text{Total number of people surveyed}} = \frac{90}{110} \approx 0.818 \][/tex]

6. Probability of a person preferring pirates:
[tex]\[ P(\text{pirate}) = \frac{\text{Total number of people who prefer pirates}}{\text{Total number of people surveyed}} = \frac{80}{110} \approx 0.727 \][/tex]

7. Conditional probability of a person being a student given they prefer pirates:
[tex]\[ P(\text{student} \mid \text{pirate}) = \frac{\text{Number of students who prefer pirates}}{\text{Total number of people who prefer pirates}} = \frac{75}{80} = 0.9375 \][/tex]

### Analysis of Independence:
To check for independence, we compare [tex]\(P(\text{student})\)[/tex] and [tex]\(P(\text{student} \mid \text{pirate})\)[/tex]. If the events are independent, these probabilities should be equal.

We have:
[tex]\[ P(\text{student}) \approx 0.818 \][/tex]
[tex]\[ P(\text{student} \mid \text{pirate}) = 0.9375 \][/tex]

Since [tex]\(P(\text{student}) \approx 0.818\)[/tex] and [tex]\(P(\text{student} \mid \text{pirate}) = 0.9375\)[/tex] are not equal, the events are not independent.

### Conclusion:
The correct answer is:
C. No, they are not independent because [tex]\(P(\text{student}) \approx 0.82\)[/tex] and [tex]\(P(\text{student} \mid \text{pirate}) \approx 0.94\)[/tex].