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Terry \& Sons makes bearings for autos. The production system involves two independent processing machines so that each bearing passes through these two processes. The probability that the first processing machine is not working properly at any time is \(.08\), and the probability that the second machine is not working properly at any time is \(.06\). Find the probability that both machines will not be working properly at any given time.

Short Answer

Expert verified
The probability that both machines will not be working properly at any given time is \( .0048 \)

Step by step solution

01

Identify the probabilities of individual events

The probability that the first processing machine is not working properly at any time is \( .08 \), denoted by \( P(A) \). Likewise, the probability that the second machine is not working properly at any time is \( .06 \), denoted by \( P(B) \).
02

Use the multiplication rule for independent events

The multiplication rule for independent events states that the joint probability of two independent events can be obtained by multiplying their individual probabilities: \( P(A \cap B) = P(A)P(B) \). Apply this rule to the given situation.
03

Compute the joint probability

Compute \( P(A \cap B) \) by simply multiplying \( P(A) \) and \( P(B) \). So, \( P(A \cap B) = .08 \times .06 = .0048 \).

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Key Concepts

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

Independent Events
When discussing independent events in probability theory, we are referring to scenarios where the outcome of one event does not affect the outcome of another. Here, each event is unaffected by the others, meaning their probabilities remain constant regardless of other occurrences. In real-world applications, this is crucial for predicting outcomes across multiple scenarios without overlap.

With the problem involving Terry & Sons, the two processing machines are said to be independent. This simply means that whether or not the first machine is working properly does not change the likelihood of the second machine functioning correctly. Understanding independence helps in setting a basis for most probability calculations, including the computation of the joint probability of both events occurring together.
Joint Probability
The concept of joint probability focuses on finding the likelihood of two or more events occurring together. In the context of Terry & Sons, we want to find the probability of both machines not working at the same time.

To find the joint probability, it's essential to determine if the events are independent or dependent. Since the events are independent, the effect one machine has on the other is none, simplifying our calculations. The joint probability of independent events is calculated by taking the product of their individual probabilities.
  • This method ensures accuracy as long as we confirm independence.
  • In our case, finding the joint probability involved multiplying 0.08 (probability of the first machine not working) by 0.06 (probability of the second machine not working).
Understanding joint probability is key not just in theoretical scenarios, but also in everyday applications where multiple independent variables are analyzed together.
Multiplication Rule
The multiplication rule is a widely used principle in probability theory, particularly effective with independent events. It states that the probability of both events A and B occurring is the product of their individual probabilities, when the events are independent.

In relation to Terry & Sons, the multiplication rule allows us to calculate the probability that both processing machines are malfunctioning at the same time. By using this rule, we multiply the two independent probabilities to find the desired joint probability:

\[P(A \cap B) = P(A) \cdot P(B) = 0.08 \times 0.06 = 0.0048\]

Key points to remember:
  • The multiplication rule is simple and effective for independent events, allowing easy computation of combined probabilities.
  • This approach streamlines calculations where independence is confirmed, making it a powerful tool in statistics and everyday decision-making.
Understanding how to apply this rule can greatly simplify problem-solving involving multiple events.

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Most popular questions from this chapter

Two thousand randomly selected adults were asked if they think they are financially better off than their parents. The following table gives the two- way classification of the responses based on the education levels of the persons included in the survey and whether they are financially better off, the same as. or worse off than their parents. $$\begin{array}{lccc} \hline & \begin{array}{c} \text { Less Than } \\ \text { High School } \end{array} & \begin{array}{c} \text { High } \\ \text { School } \end{array} & \begin{array}{c} \text { More Than } \\ \text { High School } \end{array} \\ \hline \text { Better off } & 140 & 450 & 420 \\ \text { Same as } & 60 & 250 & 110 \\ \text { Worse off } & 200 & 300 & 70 \\ \hline \end{array}$$ a. Suppose one adult is selected at random from these 2000 adults. Find the following probabilities. i. \(P\) (better off and high school) ii. \(P(\) more than high school and worse off ) b. Find the joint probability of the events "worse off" and "better off." Is this probability zero? Explain why or why not.

A restaurant chain is planning to purchase 100 ovens from a manufacturer, provided that these ovens pass a detailed inspection. Because of high inspection costs, 5 ovens are selected at random for inspection. These 100 ovens will be purchased if at most 1 of the 5 selected ovens fails inspection. Suppose that there are 8 defective ovens in this batch of 100 ovens. Find the probability that the batch of ovens is purchased. (Note: In Chapter 5 you will learn another method to solve this problem.)

The probability that a farmer is in debt is \(.80 .\) What is the probability that three randomly selected farmers are all in debt? Assume independence of events.

In a political science class of 35 students, 21 favor abolishing the electoral college and thus electing the President of the United States by popular vote. If two students are selected at random from this class, what is the probability that both of them favor abolition of the electoral college? Draw a tree diagram for this problem.

Two thousand randomly selected adults were asked whether or not they have ever shopped on the Internet. The following table gives a two-way classification of the responses. $$\begin{array}{lcc} \hline & \text { Have Shopped } & \text { Have Never Shopped } \\ \hline \text { Male } & 500 & 700 \\ \text { Female } & 300 & 500 \end{array}4$ a. If one adult is selected at random from these 2000 adults, find the probability that this adult i. has never shopped on the Internet ii. is a male iii. has shopped on the Internet given that this adult is a female iv. is a male given that this adult has never shopped on the Internet b. Are the events "male" and "female" mutually exclusive? What about the events "have shopped" and "male?" Why or why not? c. Are the events "female" and "have shopped" independent? Why or why not?

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