Consider 6 different-color marbles that are randomly selected. Create a scenario for event A and a scenario for event B , such that P(A and B)=130 . State the result of event A , the result of event B , and explain if the two events are independent or dependent.(4 points)

1 answer

To create a scenario involving the selection of 6 different-color marbles, let's define two events, A and B, based on specific outcomes related to the marbles.

Scenario for Event A:

Let event A represent the event of selecting 2 red marbles from a set of 6 marbles where there are, for example, 2 red marbles and 4 marbles of different colors (blue, green, yellow, and purple).

Result of Event A: The outcome of event A occurs if the selected marbles include exactly 2 red marbles.

Scenario for Event B:

Let event B represent the event of selecting at least 1 blue marble from the same set of 6 marbles.

Result of Event B: The outcome of event B occurs if at least 1 blue marble is included among the selected marbles.

Probability of Events:

For the sake of this example, we'll denote the probability of each event:

  • The probability of event A, \( P(A) \): Let's assume \( P(A) = 0.5 \) for this scenario (i.e., there is a 50% chance to pick 2 red marbles).
  • The probability of event B, \( P(B) \): Let's assume \( P(B) = 0.6 \) (i.e., there is a 60% chance to pick at least 1 blue marble).

Joint Probability:

To analyze the dependency of events A and B, we need \( P(A \text{ and } B) \).

Suppose through the construction of our probability calculations or through a given problem, we find that \( P(A \text{ and } B) = 0.13 \) (i.e., there is a 13% chance that we can select both 2 red marbles and at least 1 blue marble).

Independence or Dependence:

Events A and B are independent if the occurrence of one does not affect the occurrence of the other, which mathematically translates to:

\[ P(A \text{ and } B) = P(A) \times P(B) \]

Calculating the right side:

\[ P(A) \times P(B) = 0.5 \times 0.6 = 0.30 \]

Since \( P(A \text{ and } B) = 0.13 \) does not equal \( P(A) \times P(B) = 0.30 \), this implies that events A and B are dependent. The occurrence of selecting 2 red marbles impacts the probability of selecting at least one blue marble.

Summary:

  • Event A: Selecting 2 red marbles.
  • Event B: Selecting at least 1 blue marble.
  • \( P(A \text{ and } B) = 0.13 \)
  • Events A and B are dependent.