/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 2 Response Rates for Random Digit ... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Response Rates for Random Digit Dialing. When an opinion poll uses random digit dialing to select respondents for polls, the response rate is approximately \(10 \%\) for people contacted by cell phone. You watch a pollster dial cell numbers that have been selected in this manner. \(X\) is the number of calls dialed before the pollster obtains a second response to the poll.

Short Answer

Expert verified
Use a negative binomial distribution with \( p = 0.1 \) for 2 successes to model the number of calls needed for the second response.

Step by step solution

01

Understanding the Problem

In this problem, we are dealing with a geometric distribution. Here, the situation is defined by repeatedly dialing cell phone numbers, where we have a success probability of obtaining a response, denoted by \( p = 0.1 \). We want to find the number of calls needed for the second success, i.e., the second response.
02

Identifying the Distribution

Since we're looking for the number of trials until the second success, this is a scenario described by the negative binomial distribution. Specifically, when finding the number of trials needed for a given number of successes, a negative binomial distribution is appropriate.
03

Setting Up the Formula

The probability that the \( n \)-th number dialed results in the second success in a sequence of calls can be calculated using the negative binomial probability formula: \[P(X = n) = \binom{n-1}{k-1} \cdot p^k \cdot (1-p)^{n-k}\]Where \(k\) is the number of successes (in this case, 2), \( p \) is the probability of a successful response, and \(n\) is the total number of trials.
04

Calculating the Specific Probability

To find the probability of dialing \( n \) numbers to get exactly the second response, substitute \( k = 2 \) and \( p = 0.1 \) into the formula: \[P(X = n) = \binom{n-1}{1} \cdot (0.1)^2 \cdot (0.9)^{n-2}\]This expression gives the probability for any \( n \), the number of calls needed to achieve the second response.
05

Generalization and Expectations

Although the problem doesn't request a specific number \( n \), this setup can be used to calculate it for any scenario where you desire the probability of the 2nd success after \( n \) dials, and it effectively models the random dialing scenario the pollster is facing.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Geometric Distribution
The Geometric Distribution is an essential concept in probability and statistics when dealing with independent, repeated trials. It is used to determine the probability of the first occurrence of success on a given trial. In other words, it helps to identify how many trials are necessary for the first success given a constant probability of success in each trial.
- This distribution is characterized by a single parameter, the probability of success denoted by \( p \).
- The probability of achieving the first success on the \( n \)-th trial is given by: \[ P(X = n) = (1-p)^{n-1} \cdot p \]
This equation forms the backbone of the calculation, and understanding it can help in scenarios like quality control, gaming strategies, and more.
In the initial exercise, the concept extends from geometric to negative binomial, where we seek not just the first but the second success.
Probability of Success
In probability theory, the 'Probability of Success' is a fundamental measure that quantifies the likelihood of an event occurring. It is symbolized by \( p \) and a critical component in many statistical models, including the geometric and negative binomial distributions.
- A probability value (\( p \)) ranges between 0 and 1.
- For instance, in this exercise, the probability of obtaining a response during a random digit dialing is \( p = 0.1 \) or 10%.
- This probability value remains constant across all trials, as assumed in the negative binomial and other related distributions.
Understanding this probability helps in predicting outcomes and optimizing processes, such as improving the strategies in polls or surveys where responses are crucial.
Random Digit Dialing
Random Digit Dialing (RDD) is a statistical technique commonly used in opinion polling, survey sampling, and market research. It involves calling telephone numbers randomly generated to reach a representative sample of people.
- RDD helps in minimizing sampling bias since every person with a phone number has an equal chance of being selected.
- This method is especially useful when the population has no existing contact list or if a broad representative sample is needed.
- In our exercise scenario, RDD was used to gather responses, with a specific struggle being the low probability of obtaining a response (10%).
Thus, understanding RDD is crucial for appreciating how data collection methods can influence the results and reliability of statistical findings.
Statistical Modeling
Statistical Modeling is the process of applying statistical analysis to a real-life situation, using data to build a model that predicts future trends or simulates different scenarios. It provides insights and aids in decision-making.
- It involves selecting appropriate variables, distributions, and assumptions to create a model reflecting the system being studied.
- In the context of this exercise, using a negative binomial distribution to model the number of calls needed reflects the real-world contact success rate of polls.
- This approach allows predictions about how many calls a pollster might make before getting a certain number of responses, enabling better resource allocation and strategy planning.
Overall, statistical modeling helps translate theoretical distributions into practical applications, highlighting the role of assumptions and choices in interpreting results.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Binomial Setting? In each of the following situations, is it reasonable to use a binomial distribution for the random variable \(X\) ? Give reasons for your answer in each case. a. An auto manufacturer chooses one car from each hour's production for a detailed quality inspection. One variable recorded is the count \(X\) of finish defects (dimples, ripples, etc.) in the car's paint. b. The pool of potential jurors for a murder case contains 100 persons chosen at random from the adult population of a large city. Each person in the pool is asked whether he or she opposes the death penalty; \(X\) is the number who say Yes. c. Joe buys a ticket in his state's Pick 3 lottery game every week; \(X\) is the number of times in a year that he wins a prize.

Estimating \(\pi\) from Random Numbers. Kenyon College student Eric Newman used basic geometry to evaluate software random number generators as part of a summer research project. He generated 2000 independent random points \((X, Y)\) in the unit square. (That is, \(X\) and \(Y\) are independent random numbers between 0 and 1 , each having the density function illustrated in Eigure \(12.5\) (page 284). The probability that \((X, Y)\) falls in any region within the unit square is the area of the region.) 13 a. Sketch the unit square, the region of possible values for the point \((X, Y)\). b. The set of points \((X, Y)\) where \(X^{2}+Y^{2}<1\) describes a circle of radius 1. Add this circle to your sketch in part (a) and label the intersection of the two regions \(A\). c. Let \(T\) be the total number of the 2000 points that fall into the region \(A\). T follows a binomial distribution. Identify \(n\) and \(p\). (Hint: Recall that the area of a circle is \(\pi r^{2}\).) d. What are the mean and standard deviation of T? e. Explain how Eric used a random number generator and the facts given here to estimate \(\pi\).

College A dmissions. A small liheral arts college in Ohio would like to have an entering class of 500 st udents next year. Past experience shows that about \(40 \%\) of the students admitted will decide to attend. The college is planning to admit 1250 students. Suppose that students make their decisions independently and that the probability is \(0.40\) that a randomly chosen student will accept the offer of admission. a. What are the mean and standard deviation of the number of students who accept the admissions offer from this college? b. Using the Normal approximation, what is the probability that the college gets more students than it wants? Check that you can safely use the approximation. c. Use software or an online binomial calculator to compute the exact probability that the college gets more students than it wants. How good is the approximation in part (b)? d. To decrease the probability of getting more students than are wanted, does the college need to increase or decrease the number of students it admits? Using software or an online binomial calculator, what is the largest number of students that the college can admit if administrators want the exact probability of getting more students than they want to be no larger than \(5 \%\) ?

Larry reads that half of all super jumbo eggs contain double yolks. So he always buys super jumbo eggs and uses two whenever he cooks. If eggs do or don't contain two yolks independently of each other, the number of eggs with double yolks when Larry uses two chosen at random has the distribution a. binomial with \(n=2\) and \(p=1 / 2\). b. binomial with \(n=2\) and \(p=1 / 3\). c. binomial with \(n=3\) and \(p=1 / 2\).

Antibiotic Resist ance. According to CDC estimates, at least \(2.8\) million people in the United States are sickened each year with antibiotic-resistant infections, and at least 35,000 die as a result. Antibiotic resistance occurs when disease-causing microbes become resistant to antibiotic drug therapy. Because this resistance is typically genetic and transferred to the next generations of microbes, it is a very serious public health problem. Of the infections considered most serious by the CDC, gonorrhea has an estimated \(1.14\) million new cases occurring annually, and approximately \(50 \%\) of those cases are resistant to any antibiotic. \({ }^{7}\) A public health clinic in California sees eight patients with gonorrhea in a given week. a. What is the distribution of \(X\), the number of these eight cases that are resistant to any antibiotic? b. What are the mean and standard deviation of \(X\) ? c. Find the probability that exactly one of the cases is resistant to any antibiotic. What is the probability that at least one case is resistant to any antibiotic? (Hint: It is easier to first find the probability that exactly zero of the eight cases were resistant.)

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.