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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 National Public Radio show Car Talk has a feature called "The Puzzler." Listeners are asked to send in answers to some puzzling questions-usually about cars but sometimes about probability (which, of course, must account for the incredible popularity of the program!). Suppose that for a car question, 800 answers are submitted, of which 50 are correct. a. Suppose that the hosts randomly select two answers from those submitted with replacement. Calculate the probability that both selected answers are correct. (For purposes of this problem, keep at least five digits to the right of the decimal.) b. Suppose now that the hosts select the answers at random but without replacement. Use conditional probability to evaluate the probability that both answers selected are correct. How does this probability compare to the one computed in Part (a)?

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Delayed diagnosis of cancer is a problem because it can delay the start of treatment. The paper "Causes of Physician Delay in the Diagnosis of Breast Cancer" (Archives of Internal Medicine \([2002]: 1343-1348)\) examined possible causes for delayed diagnosis for women with breast cancer. The accompanying table summarizes data on the initial written mammogram report (benign or suspicious) and whether or not diagnosis was delayed for 433 women with breast cancer. $$ \begin{array}{l|cc} & & \text { Diagnosis } \\ & \begin{array}{c} \text { Diagnosis } \\ \text { Delayed } \end{array} & \begin{array}{c} \text { Not } \\ \text { Delayed } \end{array} \\ \hline \begin{array}{l} \text { Mammogram Report Benign } \\ \text { Mammogram Report } \\ \text { Suspicious } \end{array} & 32 & 89 \\ & 8 & 304 \\ \hline \end{array} $$ Consider the following events: \(B=\) the event that the mammogram report says benign \(S=\) event that the mammogram report says suspicious \(D=\) event that diagnosis is delayed a. Assume that these data are representative of the larger group of all women with breast cancer. Use the data in the table to find and interpret the following probabilities: i. \(\quad P(B)\) ii. \(P(S)\) iii. \(P(D \mid B)\) iv. \(P(D \mid S)\) b. Remember that all of the 433 women in this study actually had breast cancer, so benign mammogram reports were, by definition, in error. Write a few sentences explaining whether this type of error in the reading of mammograms is related to delayed diagnosis of breast cancer.

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