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Consider the following events:

A. The burrito is a chicken burrito.
B. The burrito is a carne asada burrito.
C. The customer requested black beans.
D. The customer requested pinto beans.

[tex]\[
\begin{tabular}{|c|c|c|c|c|c|}
\hline
& Fish & Chicken & Carne Asada & Vegetarian & Total \\
\hline
Black Beans & 2 & 37 & 5 & 1 & 45 \\
\hline
Pinto Beans & 10 & 30 & 24 & 8 & 72 \\
\hline
No Beans & 36 & 16 & 51 & 20 & 123 \\
\hline
Total & 48 & 83 & 80 & 29 & 240 \\
\hline
\end{tabular}
\][/tex]

Which two events are independent?

A. A and C
B. A and D
C. B and C
D. B and D


Sagot :

To determine the independence of two events, we compare the joint probability of the events with the product of their individual (marginal) probabilities. Events [tex]\( X \)[/tex] and [tex]\( Y \)[/tex] are independent if and only if [tex]\( P(X \ \text{and} \ Y) = P(X) \times P(Y) \)[/tex].

Given the data from the contingency table and our recognized events:
- [tex]\(A\)[/tex]: The burrito is a chicken burrito.
- [tex]\(B\)[/tex]: The burrito is a carne asada burrito.
- [tex]\(C\)[/tex]: The customer requested black beans.
- [tex]\(D\)[/tex]: The customer requested pinto beans.

### Step-by-Step Solution:

1. Calculate the total number of samples:
[tex]\[ \text{Total count} = 240 \][/tex]

2. Calculate the marginal probabilities:
[tex]\[ P(A) = \frac{83}{240} \][/tex]
[tex]\[ P(B) = \frac{80}{240} \][/tex]
[tex]\[ P(C) = \frac{45}{240} \][/tex]
[tex]\[ P(D) = \frac{72}{240} \][/tex]

3. Calculate the joint probabilities:
[tex]\[ P(A \ \text{and} \ C) = \frac{37}{240} \][/tex]
[tex]\[ P(A \ \text{and} \ D) = \frac{30}{240} \][/tex]
[tex]\[ P(B \ \text{and} \ C) = \frac{5}{240} \][/tex]
[tex]\[ P(B \ \text{and} \ D) = \frac{24}{240} \][/tex]

4. Compare the joint probability with the product of marginal probabilities:

a. For [tex]\( A \ \text{and} \ C \)[/tex]:
[tex]\[ P(A \ \text{and} \ C) \neq P(A) \times P(C) \][/tex]
[tex]\[ \frac{37}{240} \neq \frac{83}{240} \times \frac{45}{240} \][/tex]
Therefore, [tex]\( A \ \text{and} \ C \)[/tex] are not independent.

b. For [tex]\( A \ \text{and} \ D \)[/tex]:
[tex]\[ P(A \ \text{and} \ D) \neq P(A) \times P(D) \][/tex]
[tex]\[ \frac{30}{240} \neq \frac{83}{240} \times \frac{72}{240} \][/tex]
Therefore, [tex]\( A \ \text{and} \ D \)[/tex] are not independent.

c. For [tex]\( B \ \text{and} \ C \)[/tex]:
[tex]\[ P(B \ \text{and} \ C) \neq P(B) \times P(C) \][/tex]
[tex]\[ \frac{5}{240} \neq \frac{80}{240} \times \frac{45}{240} \][/tex]
Therefore, [tex]\( B \ \text{and} \ C \)[/tex] are not independent.

d. For [tex]\( B \ \text{and} \ D \)[/tex]:
[tex]\[ P(B \ \text{and} \ D) \neq P(B) \times P(D) \][/tex]
[tex]\[ \frac{24}{240} \neq \frac{80}{240} \times \frac{72}{240} \][/tex]
Therefore, [tex]\( B \ \text{and} \ D \)[/tex] are not independent.

After examining all pairs, we can confirm that none of the events [tex]\(A\)[/tex] and [tex]\(C\)[/tex], [tex]\(A\)[/tex] and [tex]\(D\)[/tex], [tex]\(B\)[/tex] and [tex]\(C\)[/tex], [tex]\(B\)[/tex] and [tex]\(D\)[/tex] are independent.

Thus, the answer is:

None of the given pairs of events are independent.