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Alejandro surveyed his classmates to determine who has ever gone surfing and who has ever gone snowboarding. Let [tex]$A$[/tex] be the event that the person has gone surfing, and let [tex]$B$[/tex] be the event that the person has gone snowboarding.

\begin{tabular}{|c|c|c|c|}
\hline & \begin{tabular}{l}
Has \\
Snowboarded
\end{tabular} & \begin{tabular}{l}
Never \\
Snowboarded
\end{tabular} & Total \\
\hline Has Surfed & 36 & 189 & 225 \\
\hline Never Surfed & 12 & 63 & 75 \\
\hline Total & 48 & 252 & 300 \\
\hline
\end{tabular}

Which statement is true about whether [tex]$A$[/tex] and [tex]$B$[/tex] are independent events?

A. [tex]$A$[/tex] and [tex]$B$[/tex] are independent events because [tex]$P(A \mid B) = P(A) = 0.16$[/tex].

B. [tex]$A$[/tex] and [tex]$B$[/tex] are independent events because [tex]$P(A \mid B) = P(A) = 0.75$[/tex].

C. [tex]$A$[/tex] and [tex]$B$[/tex] are not independent events because [tex]$P(A \mid B) = 0.16$[/tex] and [tex]$P(A) = 0.75$[/tex].

D. [tex]$A$[/tex] and [tex]$B$[/tex] are not independent events because [tex]$P(A \mid B) = 0.75$[/tex] and [tex]$P(A) = 0.16$[/tex].


Sagot :

To determine whether the events [tex]\(A\)[/tex] (has gone surfing) and [tex]\(B\)[/tex] (has gone snowboarding) are independent, we need to compare the probabilities [tex]\(P(A \mid B)\)[/tex] and [tex]\(P(A)\)[/tex].

### Step-by-Step Solution:

1. Calculate [tex]\(P(A)\)[/tex]:
[tex]\(P(A)\)[/tex] is the probability that a person has gone surfing.
[tex]\[ P(A) = \frac{\text{Total number of people who have gone surfing}}{\text{Total number of people surveyed}} = \frac{225}{300} = 0.75 \][/tex]

2. Calculate [tex]\(P(B)\)[/tex]:
[tex]\(P(B)\)[/tex] is the probability that a person has gone snowboarding.
[tex]\[ P(B) = \frac{\text{Total number of people who have gone snowboarding}}{\text{Total number of people surveyed}} = \frac{48}{300} = 0.16 \][/tex]

3. Calculate [tex]\(P(A \mid B)\)[/tex]:
[tex]\(P(A \mid B)\)[/tex] is the probability that a person has gone surfing given that they have gone snowboarding.
[tex]\[ P(A \mid B) = \frac{\text{Number of people who have both surfed and snowboarded}}{\text{Total number of people who have gone snowboarding}} = \frac{36}{48} = 0.75 \][/tex]

4. Determine Independence:
We compare [tex]\(P(A \mid B)\)[/tex] with [tex]\(P(A)\)[/tex]. For the events [tex]\(A\)[/tex] and [tex]\(B\)[/tex] to be independent, [tex]\(P(A \mid B)\)[/tex] should equal [tex]\(P(A)\)[/tex].
[tex]\[ P(A \mid B) = 0.75 \quad \text{and} \quad P(A) = 0.75 \][/tex]

Since [tex]\(P(A \mid B) = P(A)\)[/tex], events [tex]\(A\)[/tex] (has gone surfing) and [tex]\(B\)[/tex] (has gone snowboarding) are independent.

Therefore, the correct statement is:
[tex]\[ \text{A and B are independent events because } P(A \mid B) = P(A) = 0.75. \][/tex]