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The probability of event [tex]$A$[/tex] is [tex]$x$[/tex], and the probability of event [tex][tex]$B$[/tex][/tex] is [tex]$y$[/tex]. If the two events are independent, which condition must be true?

A. [tex]P(A \mid B)=y[/tex]

B. [tex]P(B \mid A)=x[/tex]

C. [tex]P(A \mid B)=x[/tex]

D. [tex]P(B \mid A)=xy[/tex]


Sagot :

To solve this problem, we need to understand the concept of independent events in probability theory.

Two events [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are said to be independent if the occurrence of one event does not affect the probability of the occurrence of the other event. Mathematically, if [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are independent events, the following condition holds true:

[tex]\[ P(A \mid B) = P(A) \][/tex]

This means that the probability of event [tex]\( A \)[/tex] occurring given that event [tex]\( B \)[/tex] has occurred is simply the probability of event [tex]\( A \)[/tex] occurring, unaffected by [tex]\( B \)[/tex].

Given this understanding, let's analyze the options provided:

- Option A: [tex]\( P(A \mid B)=y \)[/tex]
- This option suggests that the probability of [tex]\( A \)[/tex] given [tex]\( B \)[/tex] equals the probability of [tex]\( B \)[/tex]. This does not align with the definition of independence, which relates [tex]\( P(A \mid B) \)[/tex] to [tex]\( P(A) \)[/tex], not [tex]\( P(B) \)[/tex].

- Option B: [tex]\( P(B \mid A)=x \)[/tex]
- This option suggests that the probability of [tex]\( B \)[/tex] given [tex]\( A \)[/tex] equals the probability of [tex]\( A \)[/tex]. This does not align with the definition of independence. The correct relation for independent events would involve comparing [tex]\( P(B \mid A) \)[/tex] to [tex]\( P(B) \)[/tex].

- Option C: [tex]\( P(A \mid B)=x \)[/tex]
- This option is in line with the definition of independence. It directly states that [tex]\( P(A \mid B) \)[/tex] equals [tex]\( x \)[/tex], which is the same as [tex]\( P(A) \)[/tex]. This matches the condition for independent events where [tex]\( P(A \mid B) = P(A) \)[/tex].

- Option D: [tex]\( P(B \mid A)=x y \)[/tex]
- This option suggests that [tex]\( P(B \mid A) \)[/tex] is the product of [tex]\( x \)[/tex] and [tex]\( y \)[/tex], which does not relate correctly to the definition of independence. The independence condition requires that [tex]\( P(A \mid B) = P(A) \)[/tex] and [tex]\( P(B \mid A) = P(B) \)[/tex], without introducing the product of [tex]\( P(A) \)[/tex] and [tex]\( P(B) \)[/tex].

Therefore, based on the condition for the independence of events, the correct answer is Option C: [tex]\( P(A \mid B)=x \)[/tex]. This satisfies the requirement that [tex]\( P(A \mid B) = P(A) \)[/tex] for independent events.