\begin{tabular}{|c|c|c|c|c|}
\hline
& X & Y & Z & Total \\
\hline
A & 10 & 80 & 61 & 151 \\
\hline
B & 110 & 44 & 126 & 280 \\
\hline
C & 60 & 59 & 110 & 229 \\
\hline
Total & 180 & 183 & 297 & 660 \\
\hline
\end{tabular}

Which statement is true about whether Z and B are independent events?

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

B. Z and B are independent events because [tex]$P(Z) = P(B)$[/tex].

C. Z and B are not independent events because [tex]$P(Z \mid B) \neq P(Z)$[/tex].

D. Z and B are not independent events because [tex]$P(Z \mid B) \neq P(B)$[/tex].



Answer :

To determine if events [tex]\( Z \)[/tex] and [tex]\( B \)[/tex] are independent, we need to check if [tex]\( P(Z \mid B) = P(Z) \)[/tex]. In other words, we must see if the probability of [tex]\( Z \)[/tex] given [tex]\( B \)[/tex] is equal to the overall probability of [tex]\( Z \)[/tex].

Let's go through the steps to determine this:

1. Calculate the joint probability [tex]\( P(Z \cap B) \)[/tex]:
- From the table, the number of outcomes where both [tex]\( Z \)[/tex] and [tex]\( B \)[/tex] occur is 126.
- The total number of outcomes is 660.
- Therefore, [tex]\( P(Z \cap B) = \frac{126}{660} \)[/tex].

2. Calculate the probability [tex]\( P(B) \)[/tex]:
- From the table, the number of outcomes where [tex]\( B \)[/tex] occurs is 280.
- The total number of outcomes is 660.
- Therefore, [tex]\( P(B) = \frac{280}{660} \)[/tex].

3. Calculate the conditional probability [tex]\( P(Z \mid B) \)[/tex]:
- [tex]\( P(Z \mid B) = \frac{P(Z \cap B)}{P(B)} \)[/tex].
- So, [tex]\( P(Z \mid B) = \frac{\frac{126}{660}}{\frac{280}{660}} = \frac{126}{280} \)[/tex].


4. Calculate the overall probability [tex]\( P(Z) \)[/tex]:
- From the table, the number of outcomes where [tex]\( Z \)[/tex] occurs is 297.
- The total number of outcomes is 660.
- Therefore, [tex]\( P(Z) = \frac{297}{660} \)[/tex].

5. Compare [tex]\( P(Z \mid B) \)[/tex] and [tex]\( P(Z) \)[/tex]:
- From our calculations:
[tex]\[ P(Z \mid B) = \frac{126}{280} = 0.45 \][/tex]
[tex]\[ P(Z) = \frac{297}{660} = 0.45 \][/tex]

As both [tex]\( P(Z \mid B) \)[/tex] and [tex]\( P(Z) \)[/tex] are equal to 0.45, these two values are indeed the same.

Therefore, [tex]\( Z \)[/tex] and [tex]\( B \)[/tex] are independent events because [tex]\( P(Z \mid B) = P(Z) \)[/tex].

Hence, the correct statement is:
- "Z and B are independent events because [tex]\( P(Z \mid B) = P(Z) \)[/tex]."