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Determine whether the events \(A\) and \(B\) are independent. $$ P(A)=.6, P(B)=.8, P(A \cap B)=.2 $$

Short Answer

Expert verified
The events A and B are not independent, because P(A ∩ B) = 0.2 is not equal to P(A) * P(B) = 0.6 * 0.8 = 0.48.

Step by step solution

01

Define the events and given probabilities

Event A: A given event with a probability, P(A) = 0.6 Event B: A given event with a probability, P(B) = 0.8 Intersection of events A and B has the probability P(A ∩ B) = 0.2.
02

Verify if the events are independent

To check the independence of events A and B, we need to verify if the probability of their intersection is equal to the product of their individual probabilities: P(A ∩ B) = P(A) * P(B) Plug in the given probabilities: 0.2 = 0.6 * 0.8 0.2 = 0.48 Since P(A ∩ B) is not equal to P(A) * P(B), the events A and B are not independent.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Independent Events
Two events are considered independent when the occurrence of one event does not affect the probability of the other event occurring. This concept is essential in probability theory because it helps determine how different events relate to one another. Additionally, understanding whether events are independent can simplify probability calculations.
For example, in our given problem, we are testing the independence of events \(A\) and \(B\) by checking the rule for independent events:
  • If \(P(A \cap B) = P(A) \times P(B)\), the events are independent.
  • Otherwise, they are dependent, meaning one event has some effect on the probability of the other.
In this case, since \(P(A \cap B) = 0.2\) and \(P(A) \times P(B) = 0.48\), these are not equal. Therefore, events \(A\) and \(B\) are not independent.
Intersection of Events
The intersection of two events, \(A\) and \(B\), represents the event where both \(A\) and \(B\) occur simultaneously. It is denoted mathematically as \(A \cap B\). Understanding intersections is crucial when calculating probabilities in situations involving multiple events.
In probability, the intersection tells us the likelihood of both events occurring together, which can be an important part of more complex problems. In our example, the intersection of events \(A\) and \(B\) is given a probability \(P(A \cap B) = 0.2\). This value indicates the relative chance that both \(A\) and \(B\) happen at the same time.
While dealing with intersections, especially in probability calculations, it is vital to be clear about whether you are analyzing the intersection correctly within the context of dependent or independent events. Only with this understanding can you accurately interpret the relationship between these events.
Probability Calculation
Probability calculation is a fundamental process in statistics and mathematics, used to determine the likelihood of various outcomes. For each scenario, the probability of an event is a number between 0 and 1, where 0 indicates impossibility and 1 means certainty.
When dealing with probabilities, there are different methods to consider, such as the multiplication rule used for independent events. In our exercise, we aim to calculate whether events are independent by comparing the calculated intersection probability to the product of individual probabilities:
  • Calculate \(P(A) \times P(B)\) to see what the expected intersection would be if the events were independent.
  • Compare this result to the given \(P(A \cap B)\).
For the given problem, the multiplication of \(P(A)\) and \(P(B)\) does not match \(P(A \cap B)\), demonstrating that the events are not independent. This process highlights how probability calculations can assist in determining the nature and relationship of events.

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Most popular questions from this chapter

A medical test has been designed to detect the presence of a certain disease. Among those who have the disease, the probability that the disease will be detected by the test is \(.95\). However, the probability that the test will erroneously indicate the presence of the disease in those who do not actually have it is .04. It is estimated that \(4 \%\) of the population who take this test have the disease. a. If the test administered to an individual is positive, what is the probability that the person actually has the disease? b. If an individual takes the test twice and both times the test is positive, what is the probability that the person actually has the disease? (Assume that the tests are independent.)

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In a survey conducted in 2007 of 1004 adults 18 yr and older, the following question was asked: How are American companies doing on protecting the environment compared with companies in other countries? The results are summarized below: $$\begin{array}{lcccc} \hline \text { Answer } & \text { Behind } & \text { Equal } & \text { Ahead } & \text { Don't know } \\ \hline \text { Respondents } & 382 & 281 & 251 & 90 \\ \hline \end{array}$$ If an adult in the survey is selected at random, what is the probability that he or she said that American companies are equal or ahead on protecting the environment compared with companies in other countries?

In a survey conducted in the fall 2006, 800 homeowners were asked about their expectations regarding the value of their home in the next few years; the results of the survey are summarized below: $$\begin{array}{lc} \hline \text { Expectations } & \text { Homeowners } \\ \hline \text { Decrease } & 48 \\ \hline \text { Stay the same } & 152 \\ \hline \text { Increase less than } 5 \% & 232 \\ \hline \text { Increase 5-10\% } & 240 \\ \hline \text { Increase more than 10\% } & 128 \\ \hline \end{array}$$ If a homeowner in the survey is chosen at random, what is the probability that he or she expected his or her home to a. Stay the same or decrease in value in the next few years? b. Increase \(5 \%\) or more in value in the next few years?

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