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An experiment consists of rolling a standard six-sided die once. Event [tex]$A$[/tex] is "rolling an even number" and event [tex]$B$[/tex] is "rolling a 2."

Are the events dependent or independent? Why? Select the option that correctly answers both questions.

A. Events [tex]$A$[/tex] and [tex]$B$[/tex] are dependent, because [tex]$P(B) \neq P(B \mid A)$[/tex]
B. Events [tex]$A$[/tex] and [tex]$B$[/tex] are dependent, because [tex]$P(A) \neq P(B \mid A)$[/tex]
C. Events [tex]$A$[/tex] and [tex]$B$[/tex] are independent, because [tex]$P(B) = P(B \mid A) = \frac{1}{6}$[/tex]
D. Events [tex]$A$[/tex] and [tex]$B$[/tex] are independent, because [tex]$P(A) = P(B \mid A) = \frac{1}{2}$[/tex]


Sagot :

To determine if events [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are dependent or independent, we need to examine the probabilities involved and compare [tex]\( P(B) \)[/tex] with [tex]\( P(B \mid A) \)[/tex]:

1. Identify the events:
- Event [tex]\( A \)[/tex]: Rolling an even number on a six-sided die. The possible outcomes are [tex]\( \{2, 4, 6\} \)[/tex].
- Event [tex]\( B \)[/tex]: Rolling a 2 on a six-sided die. The only outcome is [tex]\( \{2\} \)[/tex].

2. Calculate the probabilities:
- The probability of event [tex]\( A \)[/tex] (rolling an even number) is given by:
[tex]\[ P(A) = \frac{\text{Number of favourable outcomes for event } A}{\text{Total number of outcomes}} = \frac{3}{6} = 0.5 \][/tex]

- The probability of event [tex]\( B \)[/tex] (rolling a 2) is given by:
[tex]\[ P(B) = \frac{\text{Number of favourable outcomes for event } B}{\text{Total number of outcomes}} = \frac{1}{6} \approx 0.16667 \][/tex]

- The probability of event [tex]\( B \)[/tex] given that event [tex]\( A \)[/tex] has occurred (rolling an even number and then checking if it's a 2) is:
[tex]\[ P(B \mid A) = \frac{\text{Number of favourable outcomes for event } B \text{ within } A}{\text{Number of outcomes for event } A} = \frac{1}{3} \approx 0.33333 \][/tex]

3. Determine if events [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are dependent or independent:
- Events [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are independent if [tex]\( P(B) = P(B \mid A) \)[/tex].
- From the probabilities calculated, we have:
[tex]\[ P(B) \approx 0.16667 \quad \text{and} \quad P(B \mid A) \approx 0.33333 \][/tex]

- Since [tex]\( P(B) \neq P(B \mid A) \)[/tex], events [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are dependent.

Thus, the correct answer is:

Events [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are dependent, because [tex]\( P(B) \neq P(B \mid A) \)[/tex]