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Suppose that, starting at a certain time, batteries coming off an assembly line are examined one by one to see whether they are defective (let \(\mathrm{D}=\) defective and \(\mathrm{N}=\) not defective). The chance experiment terminates as soon as a nondefective battery is obtained. a. Give five possible experimental outcomes. b. What can be said about the number of outcomes in the sample space? c. What outcomes are in the event \(E\), that the number of batteries examined is an even number?

Short Answer

Expert verified
a. The five possible experimental outcomes could be: D, DD, DDD, N, DN. b. There is an infinite number of outcomes in the sample space as there could be an unlimited number of defective batteries before finding a non-defective one. c. The outcomes in event E, where the number of batteries examined is even, must include an odd number of 'D's followed by 'N', like N, DDDN, DDDDDN, and so on.

Step by step solution

01

Identify Experimental Outcomes

Remember that an experimental outcome is a possible result of an experiment. Here, 'D' stands for defective battery and 'N' for non-defective. As the experiment stops once a non-defective battery is found, an outcome cannot end with a 'D'. Given that, five possible outcomes could be: \[D, DD, DDD, N, DN\]. Each D indicates a defective battery found, and the first N encountered ends the experiment.
02

Identify Sample Space

The sample space is the set of all possible outcomes. In this case, the sample space is infinite, because theoretically, there could be an unlimited number of defective batteries before encountering a non-defective one. Therefore, the sample space contains all strings that start with zero or more D's and end with an N.
03

Identify Outcomes in Event E

Event E is defined as the event that the number of batteries examined (including the final non-defective one) is an even number. This can only occur if the string contains an odd number of D's before the N shows up because we are adding one non-defective battery, which makes the total count an even number. Some of the outcomes in E could thus be: \[N, DDDN, DDDDDN,....\] and so on.

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Key Concepts

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

Sample Space
When embarking on the study of probability, the concern is not just with individual outcomes, but with the entire collection of all possible outcomes, which is known as the sample space. For example, consider a simple coin toss. The sample space is quite straightforward: \( \{ H, T \} \), meaning the coin will either land on heads (H) or tails (T).

However, in more complex scenarios like the battery inspection problem from our exercise, the sample space isn't initially as apparent. Here, each outcome is a sequence of examinations ending with a non-defective battery. Even though there is a potentially infinite sequence of defective batteries before a non-defective one, any actual experiment will only involve a finite sequence. The sample space is therefore composed of all sequences which start with zero or more 'D's and end with an 'N'.

Recognizing the nature of a sample space is pivotal for understanding various probability problems. Whether finite or infinite, the sample space embodies all potential scenarios that could occur within the context of the experiment and serves as a foundation for calculating probabilities.
Probability Theory
Diving into the realm of probability theory, we uncover the mathematical framework for quantifying uncertainty associated with random phenomena. It's a field that merges rigorous logic with an element of chance. At its core is the idea that each event has a probability, a numerical value that reflects the likelihood of that event occurring.

In the context of our battery assembly line experiment, probability theory will help us comprehend the likelihood of drawing a defective battery from the line. Understanding the rules and principles of probability is essential. For instance, the probability of any event lies between 0 and 1 inclusive. Moreover, the sum of probabilities of all exhaustive, mutually exclusive events equals 1.

Interestingly, the issue of whether the probability of drawing a defective battery is independent or dependent on previous draws will influence our understanding of the experiment’s outcomes. Probability theory gives us the tools to deal with these subtleties logically and consistently.
Statistics Education
The discipline of statistics education hinges on ensuring that students are fluent in interpreting data, comprehending variability, and making informed decisions based on statistical reasoning. A solid foundational understanding is vital for navigating through more intricate statistical concepts.

Incorporating exercises, like our battery inspection problem, into a statistics curriculum can significantly enhance learning. It illustrates the practical application of concepts such as sample space and event probabilities. Learning to define the sample space correctly and to identify events within that space is crucial. Exercises should encourage students to reason abstractly about all possible outcomes and to apply probability principles thoughtfully to solve real-world problems.

For educators, the focus should be on clear explanation and relevance to real-world situations. Tailoring such exercises with step-by-step solutions can foster a deeper understanding, and when students encounter issues like infinite sample spaces, proper guidance can help them grasp these abstract concepts without feeling overwhelmed.

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Most popular questions from this chapter

The manager of a music store has kept records of the number of CDs bought in a single transaction by customers who make a purchase at the store. The accompanying table gives six possible outcomes and the estimated probability associated with each of these outcomes for the chance experiment that consists of observing the number of CDs purchased by the next customer at the store. $$ \begin{aligned} &\begin{array}{l} \text { Number of CDs } \\ \text { purchased } \end{array} & 1 & 2 & 3 & 4 & 5 & 6 \text { or more } \\ &\begin{array}{c} \text { Estimated } \\ \text { probability } \end{array} & .45 & .25 & .10 & .10 & .07 & .03 \end{aligned} $$ a. What is the estimated probability that the next customer purchases three or fewer CDs? b. What is the estimated probability that the next customer purchases at most three CDs? How does this compare to the probability computed in Part (a)? c. What is the estimated probability that the next customer purchases five or more CDs? d. What is the estimated probability that the next customer purchases one or two CDs? e. What is the estimated probability that the next customer purchases more than two CDs? Show two different ways to compute this probability that use the probability rules of this section.

Many fire stations handle emergency calls for medical assistance as well as calls requesting firefighting equipment. A particular station says that the probability that an incoming call is for medical assistance is .85. This can be expressed as \(P(\) call is for medical assistance \()=.85\). a. Give a relative frequency interpretation of the given probability. b. What is the probability that a call is not for medical assistance? c. Assuming that successive calls are independent of one another, calculate the probability that two successive calls will both be for medical assistance. d. Still assuming independence, calculate the probability that for two successive calls, the first is for medical assistance and the second is not for medical assistance. e. Still assuming independence, calculate the probability that exactly one of the next two calls will be for medical assistance. (Hint: There are two different possibilities. The one call for medical assistance might be the first call, or it might be the second call.) f. Do you think that it is reasonable to assume that. the requests made in successive calls are independent? Explain.

There are two traffic lights on the route used by a certain individual to go from home to work. Let \(E\) denote the event that the individual must stop at the first light, and define the event \(F\) in a similar manner for the second light. Suppose that \(P(E)=.4, P(F)=.3\), and \(P(E \cap F)=.15\) a. What is the probability that the individual must stop at at least one light; that is, what is the probability of the event \(E \cup F\) ? b. What is the probability that the individual needn't stop at either light? c. What is the probability that the individual must stop at exactly one of the two lights? d. What is the probability that the individual must stop just at the first light? (Hint: How is the probability of this event related to \(P(E)\) and \(P(E \cap F)\) ? A Venn diagram might help.)

The general addition rule for three events states that $$ \begin{aligned} &P(A \text { or } B \text { or } C)=P(A)+P(B)+P(C) \\ &\quad-P(A \text { and } B)-P(A \text { and } C) \\ &\quad-P(B \text { and } C)+P(A \text { and } B \text { and } C) \end{aligned} $$ A new magazine publishes columns entitled "Art" (A), "Books" (B), and "Cinema" (C). Suppose that \(14 \%\) of all subscribers read \(\mathrm{A}, 23 \%\) read \(\mathrm{B}, 37 \%\) read \(\mathrm{C}, 8 \%\) read \(\mathrm{A}\) and \(\mathrm{B}, 9 \%\) read \(\mathrm{A}\) and \(\mathrm{C}, 13 \%\) read \(\mathrm{B}\) and \(\mathrm{C}\), and \(5 \%\) read all three columns. What is the probability that a randomly selected subscriber reads at least one of these three columns?

After all students have left the classroom, a statistics professor notices that four copies of the text were left under desks. At the beginning of the next lecture, the professor distributes the four books at random to the four students \((1,2,3\), and 4\()\) who claim to have left books. One possible outcome is that 1 receives 2's book, 2 receives 4's book, 3 receives his or her own book, and 4 receives l's book. This outcome can be abbreviated \((2,4,3,1)\). a. List the 23 other possible outcomes. b. Which outcomes are contained in the event that exactly two of the books are returned to their correct owners? Assuming equally likely outcomes, what is the probability of this event? c. What is the probability that exactly one of the four students receives his or her own book? d. What is the probability that exactly three receive their own books? e. What is the probability that at least two of the four students receive their own books?

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