/*! 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} Q91E Invoice errors in a billing sys... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 6: Q91E (page 367)

Invoice errors in a billing system. In a study of invoice errors in a company鈥檚 new billing system, an auditor randomly sampled 35 invoices produced by the new system and recorded actual amount (A), invoice amount (I), and the difference (or error),x=A-I . The results were x炉=\(1ands=\)124. At the time that the sample was drawn, the new system had produced 1,500 invoices. Use this information to find an approximate 95% confidence interval for the true mean

Short Answer

Expert verified

The 95% confidence interval for true mean is (-40.92, 42.92).

Step by step solution

01

Given information

The population size is N=1500 invoices

The sample size is n = 35 invoices

The sample mean of invoices is x炉=$1

The standard deviation of the invoice iss=$124

02

Calculating a confidence interval

Consider,

nN=351500=0.02

Here, nN=0.02<0.05the finite population correction factor is not included in the calculation of the standard error.

The 95% confidence interval for the true mean is obtained by using the following formula,

x炉卤2sn

Therefore,

x炉卤2sn=1卤212435=1卤41.92=-40.92,42.92

Hence, the required confidence interval is (-40.92, 42.92), and it is 95% confident that the true mean invoice error of the new system is lies between -$40.92 and $42.92

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 91影视!

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

Zillow.com estimates of home values. Zillow.com is a real estate Web site that provides free estimates of the market value of homes. Refer to The Appraisal Journal (Winter 2010) study of the accuracy of Zillow鈥檚 estimates, Exercise 1.25 (p. 51). Data were collected for a sample of 2,045 single-family residential properties in Arlington, Texas. The researchers determined that Zillow overestimated by more than 10% the market value of 818 of the 2,045 homes. Suppose you want to estimate p, the true proportion of Arlington, Texas, homes with market values that are over-estimated by more than 10% by Zillow.

a. Find p^, the point estimate of p.

b. Describe the sampling distribution of .

c. Find a 95% confidence interval for p.

d. Give a practical interpretation of the confidence interval, part c.

e. Suppose a Zillow representative claims that p = .3. Is the claim believable? Explain.

Accountants鈥� salary survey. Each year, ManagementAccountingreports the results of a salary survey of themembers of the Institute of Management Accountants(IMA). One year, the 2,112 members responding had a salarydistribution with a 20th percentile of \(35,100; a medianof \)50,000; and an 80th percentile of \(73,000.

  1. Use this information to determine the minimum samplesize that could be used in next year鈥檚 survey toestimate the mean salary of IMA members towithin\)2,000 with 98% confidence. [Hint: To estimate s,first applyChebyshev鈥檚 Theorem to find ksuch thatat least 60% of the data fall within kstandard deviations of 渭. Then find data-custom-editor="chemistry" s鈮�(80th辫别谤肠别苍迟颈濒别鈥�20thpercentile)/2k.]
  2. Explain how you estimated the standard deviation requiredfor the sample size calculation.
  3. List any assumptions you make.

Question: Furniture brand familiarity. A brand name that consumers recognize is a highly valued commodity in any industry. To assess brand familiarity in the furniture industry, NPD (a market research firm) surveyed 1,333 women who head U.S. households that have incomes of $25,000 or more. The sample was drawn from a database of 25,000 households that match the criteria listed above. Of the 10 furniture brands evaluated, La-Z-Boy was the most recognized brand; 70.8% of the respondents indicated they were 鈥渧ery familiar鈥� with La-Z-Boy.

a. Describe the population being investigated by NPD.

b. In constructing a confidence interval to estimate the proportion of households that are very familiar with the La-Z-Boy brand, is it necessary to use the finite population correction factor? Explain.

c. What estimate of the standard error of should be used in constructing the confidence interval of part b?

d. Construct a 90% confidence interval for the true proportion and interpret it in the context of the problem.

Salmonella poisoning from eating an ice cream bar.Recently, a case of salmonella (bacterial) poisoning wastraced to a particular brand of ice cream bar, and themanufacturer removed the bars from the market. Despitethis response, many consumers refused to purchase anybrand of ice cream bars for some period of time after the event (McClave, personal consulting). One manufacturerconducted a survey of consumers 6 months after theoutbreak. A sample of 244 ice cream bar consumers wascontacted, and 23 respondents indicated that they wouldnot purchase ice cream bars because of the potential forfood poisoning.

  1. What is the point estimate of the true fraction of the entiremarket who refuse to purchase bars 6 months after the out-break?
  2. Is the sample size large enough to use the normalapproximation for the sampling distribution of the estimator of the binomial probability? Justify your response.
  3. Construct a 95% confidence interval for the true proportionof the market who still refuses to purchase icecream bars 6 months after the event.
  4. Interpret both the point estimate and confidence interval in terms of this application.

Methyl t-butyl ether (MTBE) is an organic water contaminant that often results from gasoline spills. The level of MTBE (in parts per billion) was measured for a sample of 12 well sites located near a gasoline service station in New Jersey (Environmental Science & Technology,January 2005). The data are listed in the accompanying table.

a. Give a point estimate for m, the true mean MTBE level for all well sites located near the New Jersey gasoline service station.

b. Calculate and interpret a 99% confidence interval for m.

c. What assumptions are required for the interval, part b, to be valid? Are these assumptions reasonably satisfied?
See all solutions

Recommended explanations on Math Textbooks

Mechanics Maths

Read Explanation

Applied Mathematics

Read Explanation

Logic and Functions

Read Explanation

Calculus

Read Explanation

Geometry

Read Explanation

Decision Maths

Read Explanation
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.