Question: A nationwide poll claims that the margin

> Quality control has been a problem with a new product assembly line, and a multiple regression analysis is being used to help identify the source of the trouble. The daily “percent defective” has been identified as the

> It is budgeting time again, and you would like to know the expected payoff (in terms of dollars collected) of spending an extra dollar on collection of delinquent accounts, after adjusting for the size of the pool of delinquent accounts. Identify the Y v

> For the previous problem, interpret the regression coefficient for labor by estimating the average final cost associated with each dollar that management identified ahead of time as being labor related. Data from Problem 17: Consider the computer outpu

> For the experience variable: Answer the parts of exercise 1. Data from exercise 1: For the annual salary levels: a. Find the range. b. Find the standard deviation. c. Find the coefficient of variation. d. Compare these three summary measures. What do t

> Take a close look at the data using appropriate statistical methods.

> Your firm is wondering about the results of magazine advertising as part of an assessment of marketing strategy. For each ad, you have information on its cost, its size, and the number of inquiries it generated. In particular, you are wondering if the nu

> Identify the structure of the scatterplot in Fig. 11.3.6. Fig. 11.3.6: FIG. 11.3.6

> Identify the structure of the scatterplot in Fig. 11.3.5. Fig. 11.3.5: FIG. 11.3.5

> One weekend when you reduced prices 5%, your store had $58,000 worth of sales. The next weekend, with a 15% reduction, your sales were $92,000. The weekend after that, with a 17.5% reduction, your sales were $95,000. Based on all this information, how mu

> On Monday, your business produced 7 items which cost you $18. On Tuesday, you produced 8 costing $17. On Wednesday, you produced 18 costing $32. On Thursday, you produced 3 items costing $16. Using a linear regression model accounting for fixed and varia

> Which of the following correlation coefficients corresponds to a moderately strong relationship with higher X values associated with higher Y values: r = 1, r = 0.73, r = 0.04, r = –0.83, or r = 0.99?

> One day your factory used $385 worth of electricity to produce 132 items. On a second day, $506 worth of electricity was consumed to produce 183 items. On a third day, the numbers were $261 and 105. How much electricitydoyouestimateitwouldtaketoproduce15

> Given the correlation r = 0.307 and the least-squares prediction equation Y = 55.6+18.2X, find the predicted value for Y when X is $25.

> Given the correlation r = 0.603 and the least-squares prediction equation Y = 38.2–5.3X, find the predicted value for Y when X is 15.

> For each of the scatterplots in Figs. 11.3.1–11.3.4, say whether the correlation is closest to 0.9, 0.5, 0.0, 0.5, or 0.9. Fig. 11.3.1: Fig. 11.3.4: FIG. 11.3.1 FIG. 11.3.4

> For the ages: Answer the parts of exercise 2. Data from exercise 2: For the annual salary levels: a. Construct a histogram and indicate the average and standard deviation. b. How many employees are within one standard deviation from the average? How do

> Find the critical t value that would be used to construct the confidence interval for the slope coefficient in a regression analysis for each of the following situations: a. For 95% confidence, based on a sample size of n = 298. b. For 99% confidence, ba

> The least-squares prediction equation is, predicted costs = 35.2+5.3 (items), with predicted costs measured in dollars. Find the predicted value and residual for a situation with costs of $600 and 100 items.

> a. Why is a two-sided test appropriate for the previous problem? b. State the one-sided result of the two-sided test at the 5% level, if appropriate. Data from Problem 5: Some of your advertisements seem to get no reaction, as though they are being ign

> a. Why is a two-sided test appropriate for the previous problem? b. State the one-sided result of the two-sided test at the 5% level, if appropriate.

> Production yields vary and can be high or low on a given day. If they are high, you want to find out why so that yields could be similarly increased on other days. If they are low, you want to fix the problem. You have just learned that today’s productio

> Here are the satisfaction scores given by 12 randomly selected customers: 89, 98, 96, 65, 99, 81, 76, 51, 82, 90, 96, 76 Does the observed average score differ significantly from the target score of 80? Justify your answer.

> Test whether or not the population percentage could reasonably be 20%, based on the observed 18.4% who like your products, from a random sample of 500 consumers.

> A recent poll of 809 randomly selected registered voters revealed that 426 plan to vote for your candidate in the coming election. a. Is the observed percentage more than 50%? b. Is the observed percentage significantly more than 50%? How do you know? Ba

> Do initial public offerings (IPOs) of stock significantly increase in value, on average, in the short term? Test using the data from Table 4.3.7 that show performance of initial offerings as percent increases from the offer price, with most newly traded

> The p-value is 0.0371. What conclusions can you reach and what error might have been made?

> For the ages: Answer the parts of exercise 1. Data from exercise 1: For the annual salary levels: a. Find the range. b. Find the standard deviation. c. Find the coefficient of variation. d. Compare these three summary measures. What do they tell you ab

> Production yield data with 17 degrees of freedom have been collected. Find the critical t value to use for each of the following confidence interval calculations: a. One-sided 95% confidence. b. One-sided 99% confidence. c. One-sided 99.9% confidence. d.

> Consumer preferences have been observed in a situation for which the standard error is known. Find the critical t value to use for each of the following confidence interval calculations: a. Two-sided 95% confidence. b. Two-sided 99% confidence. c. Two-si

> Vaccine responses have been observed for1,859 people. Find the critical t value to use for each of the following confidence interval calculations: a. Two-sided 95% confidence. b. Two-sided 99% confidence. c. Two-sided 99.9% confidence. d. Two-sided 90% c

> Cost observations have been provided for 21 production situations. Find the critical t value to use for each of the following confidence interval calculations: a. Two-sided 95% confidence. b. Two-sided 99% confidence. c. Two-sided 99.9% confidence. d. Tw

> Intensities have been measured for eight flashlights. Find the critical t value to use for each of the following confidence interval calculations: a. Two-sided 95% confidence. b. Two-sided 99% confidence. c. Two-sided 99.9% confidence. d. Two-sided 90% c

> The amount of caffeine (milligrams) in randomly sampled cups of coffee was as follows: 112:8,86:4, 45:9,110: 3, 100:3,93:3, 101:9,115:7,92:5,117:3,105:6,81:6 a. Find the one-sided 99% confidence interval for the population mean caffeine content of a cup

> From a list of the 729 people who went on a cruise, 130 were randomly selected for interview. Of these, 112 said that they were very happy with the accommodations. Find the 95% confidence interval for the population percentage who would have said they we

> Find the one-sided 95% confidence interval for the weight of candy bars after intervention, based on the data in Table 5.5.4, indicating that the population mean weight is no more than some amount. Table 5.5.4: TABLE 5.5.4 Weight (in Ounces) for Tw

> Find the 99.9% confidence interval for the weight of candy bars before intervention, based on the data in Table 5.5.4 of Chapter 5. Table 5.5.4: TABLE 5.5.4 Weight (in Ounces) for Two Samples of Candy Bars Before Before After After Intervention Int

> Find the 99% confidence interval for the strength of cotton yarn used in a weaving factory based on the data in problem 23 of Chapter 4. Data from problem 23: Consider the strength of cotton yarn used in a weaving factory, in pounds of force at breakag

> For the annual salary levels: a. Construct a histogram and indicate the average and standard deviation. b. How many employees are within one standard deviation from the average? How does this compare to what you would expect for a normal distribution? c.

> Find the 95% confidence interval for the amounts that your regular customers spent on your products last month, viewing the data from Table 4.3.1 of Chapter 4 as a random sample of customer orders. Table 4.3.1: TABLE 4.3.1 Last Month's Sales Custom

> Your quality control department has just analyzed the contents of 20 randomly selected barrels of materials to be used in manufacturing plastic garden equipment. The results found an average of 41.93 gallons of usable material per barrel, with a standard

> A market survey has shown that people will spend an average of $2.34 each for your product next year, based on a sample survey of 400 people. The standard deviation of the sample was $0.72. Find the two-sided 95% confidence interval for next year’s mean

> Your hospital is negotiating with medical insurance providers, who would like to reduce the amount they pay as reimbursement for hospital stays. For a particular procedure, they would like to reduce payment by $300 and have patients go home one day earli

> Based on the following daily percent changes of the S&P 500 stock market index for June 2010 (accessed at http:// finance.Yahoo.com on July 13,2010), find the 95% confidence interval for the population mean daily change. (This is not, strictly speaking,

> Comparison shopping is available on the Internet, and this is useful because exactly the same item is available at a variety of prices. Table 9.6.1 shows results from My Simon for prices of the Eureka 4750A Bagged Upright Vacuum at 15 stores. Find the 95

> Your firm is in the market to hire an experienced vice president of information technology or information systems. If one is chosen at random from the population represented in the preceding problem, complete the following sentence: We are 99% sure that

> A survey of eight vice presidents of information technology and information systems, who had been in their current positions for 10 years or less, revealed $174,813 as the average salary.15 Assume a random sample with a standard deviation of $25,000. a.

> A survey of 21 business intelligence analysts, who had been in their current positions from 10 to 20 years, revealed $90,734 as the average salary.14 Assume a random sample with a standard deviation of $15,000. a. Find the 95% confidence interval for the

> A nationwide poll claims that the margin of error is no more than 4.3 percentage points for questions asked of half the sample (at the 95% confidence level). a. Verify this claim in a particular case by computing the critical t value times the standard e

> For the annual salary levels: a. Find the range. b. Find the standard deviation. c. Find the coefficient of variation. d. Compare these three summary measures. What do they tell you about typical salaries in this administrative division?

> In a sample of 258 individuals selected randomly from a city of 750,339 people, 165 were found to be supportive of a new public works project. Find the99.9%confidence interval for the support level percentage in the entire city.

> A recent survey of 252 customers, selected at random from a database with 12,861 customers, found that 208 are satisfied with the service they are receiving. Find the 99% confidence interval for the percentage satisfied for all customers in the database.

> Your company prepares and distributes frozen foods. The package claims a net weight of 24.5 oz. A random sample of today’s production was weighed, and the results were summarized as follows: average = 24.41 oz, standard deviation = 0.11 oz, sample size =

> Your company is planning to market a new reading lamp and has segmented the market into three groups: avid readers, regular readers, and occasional readers. As part of a marketing survey, 400 individuals have been randomly selected from the population of

> A market survey has shown that people will spend an average of $15.48 each for your product next year, based on a sample survey of 483 people. The standard deviation of the sample was $2.52. Find the two-sided 95% confidence interval for next year’s mean

> Your bakery produces loaves of bread with “1 pound” written on the label. Here are weights of randomly sampled loaves from today’s production: 1:02,0:97,0:98,1:10,1:00,1:02 0:98,1:03,1:03,1:05,1:02,1:06 Find the 95% confidence interval for the mean weigh

> View the 989 donors in the donations database (out of 20,000 people represented on the companion site) as a random sample from a much larger population of people who would make a donation in response to the mailing. Note that the column of 989 donation a

> A random sample of eight customers was interviewed in order to find the number of computers they planned to order next year. The results were 22, 18, 24, 47, 64, 32, 45, and 35. You are interested in knowing about the larger population that these custome

> Main-course taste scores have been recorded for 48 restaurant diners on a scale from 1 to 5. The average score was 4.125, the standard error was 0.1099, and the 95% confidence interval extended from 3.904 to 4.346. Find the margin of error.

> For the ages: Answer the parts of exercise 2. Data from exercise 2: For the annual salary levels: a. Construct a cumulative distribution function. b. Find the median, quartiles, and extremes. c. Construct a box plot, and comment on its appearance. d. F

> Your agricultural firm is considering the purchase of some farmland, and an indication of the quality of the land will be helpful. A random sample of 62 selected locations planted with corn indicates an average yield of 103.6 bushels per acre, with a sta

> Draw a random sample off our firms from a population of 86 suppliers, starting with row 30, column 4 of the table of random digits.

> Draw a random sample of three account numbers from a population of 681 accounts receivable documents, starting with row 6, column 2 of the table of random digits.

> Select a random sample of four without replacement from the following metal products corporations: Gillette, Crown Cork & Seal, MASCO, Tyco Laboratories, Illinois Tool Works, McDermott, Ball, Stanley Works, Harsco, Hillenbrand Industries, Newell, Snap-on

> Select a random sample of three without replacement from the following (very small) population of firms: IBM, GM, Ford, Shell, HP, Boeing, and ITT. Use the following sequence of random digits:5887053671352339.

> You have chosen a sample of 25 supermarkets out of the 684 you have responsibility for. These 25 have been inspected, and the number of violations of company policy has been recorded. For each of the following quantities, state whether it is a statistic

> From a list of the 729 people who went on a cruise, 25 were randomly selected for interview. Of these, 21 said that they were “very happy” with the accommodations. a. What percent of the sample said that they were “very happy”? b. If you had been able to

> Based on careful examination of a sample of size 868 taken from 11,013 inventory items in a warehouse, you learn that 3.6% are not ready to be shipped. a. Find the standard error associated with this estimated percentage and indicate its meaning. b. Woul

> Consider an election poll designed so that each household has an equal chance of being selected and one registered voter is interviewed from each selected household. Analyze what would happen if single-voter households were more likely to vote Democratic

> In a study of brand recognition, out of 763 people chosen at random, 152 were unable to identify your product. a. Estimate the percentage of the population (from which this sample was taken) who would be unable to identify your product. b. Find the stand

> For the ages: Answer the parts of exercise 1. Data from exercise 1: For the annual salary levels: a. Find the average. b. Find the median. c. Construct a histogram, and give an approximate value for the mode. d. Compare these three summary measures. Wh

> A survey of 823 randomly selected adults in the United States finds that 63% support current government policies. Find the usual measure that indicates approximately how far this sample percentage is from the value that would have been found if all adult

> Find the average and the standard error for the weight of candy bars before intervention, based on the data in Table 5.4 of Chapter 5. Table 5.5.4: TABLE 5.5.4 Weight (in Ounces) for Two Samples of Candy Bars Before Before After After Intervention

> Find the average and the standard error for the strength of cotton yarn used in a weaving factory, based on the data in problem 23 of Chapter 4. Data from problem 23: Consider the strength of cotton yarn used in a weaving factory, in pounds of force at

> Find the average and the standard error for the amounts that your regular customers spent on your products last month, viewing the data from problem 2 of Chapter 4 as a sample of customer orders. Data from problem 2: Table 4.3.1 provides a list of the

> A random sample of 50 recent patient records at a clinic shows that the average billing per visit was $53.01 and the standard deviation was $16.48. a.* Find the standard error of the average and interpret it. b. You feel that this standard error is too l

> Find the standard error of the average for the following data set representing quality of agricultural produce: 16:7,17:9,23:5,13:8,15:9,15:2,12:9,15:7

> The sample average age is 69.8 and the sample standard deviation is 9.2, based on a sample of 200 individuals in a retirement community. Your friend claims that “the sample average is approximately 9.2 away from the population mean.” Is your friend corre

> Which of the following samples is likely to be the most representative of the population of all employees at IBM? a. The 10 oldest and most experienced researchers at the Thomas J. Watson Research Center. b. A random sample of 10 computer repair speciali

> Your customers’ average order size is $2,601, with a standard deviation of $1,275. You are wondering what would happen if exactly 45 typical customers independently placed orders tomorrow. a.* Find the mean of tomorrow’s total orders. b.* Find the standa

> A typical incoming telephone call to your catalog sales force results in a mean order of $28.63 with a standard deviation of $13.91. You may assume that orders are received independently of one another. a. Based only on this information, can you find the

> For the genders: a. Summarize by finding the percent of each category. b. Find the mode. What does this tell you?

> You have analyzed a project using four scenarios, with the results shown in Table 8.6.1. Suppose you actually have 40 projects just like this one and they pay off independently of one another. Find the probability that your average profit per project wil

> The population mean is$65 and the population standard deviation is $30. Find the probability that the average of 35 randomly selected transactions is between $55 and $60. You may assume that the population is approximately normally distributed.

> A farmer has five identical cornfields, each of which independently produces a normally distributed harvest with a mean of 80,000 bushels and a standard deviation of 15,000 bushels. Find the probability that the average harvest for the five fields will e

> Breakfast cereal is packed into packages labeled “net weight 20 ounces, packed by weight not by volume; some settling may occur during shipment.” However, weights of individual packages are not really all exactly equal to 20 oz—although they are close, t

> Which of the following samples is likely to be the most representative of the population of all registered voters in the United States? a. A sample of 200 people at a Denver shopping mall. b. A sample of 200 of your friends and their friends. c. A sample

> You have a factory with 40 production machines that are essentially identical, each producing at a mean daily rate of 90 products with a standard deviation of 35. You may assume that they produce independently of one another. Consider the random variable

> You have interviewed 369 people out of a population of 30,916 and found that 51.8% expect to vote for the challenger in the upcoming election. Find the standard error of this estimate.

> Deposits have a mean of $125 and a standard deviation of $36. Find the standard deviation of the average amount of 12 randomly selected deposits.

> You have estimated the inventory value of your competition as $384,000 but later learn that the true inventory value was $416,000. Find the estimation error.

> You have eight machines operating independently. The mean production rate for each machine is 20.3 tons/day, and the standard deviation is 1.4 tons/day. Approximately how much uncertainty is there in the average daily production for the eight machines? P

> For the annual salary levels: a. Construct a cumulative distribution function. b. Find the median, quartiles, and extremes. c. Construct a box plot, and comment on its appearance. d. Find the 10th percentile and the 90th percentile. e. What is the percen

> The population mean productivity is 35, the population standard deviation is 10, and the sample size is 15. Find the standard deviation of the total amount represented by a random sample.

> The mean account balance is $500 and the standard deviationis$120foralargepopulation of bank accounts. Find the standard deviation of the average balance of groups of eight accounts (chosen independently of one another and with equal probabilities of sel

> Draw a random sample of eight invoices from a population of 500 overdue billings, starting with row 17, column 5 of the table of random digits.

> Draw a random sample of five contracts from a population of 362 recent contracts with cost overruns, starting with row 13, column 5 of the table of random digits.

> You are planning to invest in a new high-tech company, and figure your rate of return over the coming year as in Table 7.6.4 (where 100% says that you doubled your money, 50% says you lost half, etc.). a. Find the mean rate of return and explain what it

> You work for the loan department of a large bank. You know that one of your customers has been having trouble with the recession and may not be able to make the loan payment that is due next week. You believe there is a 60% chance that the payment of $50

> A new project has an uncertain cash flow. A group meeting has resulted in a consensus that a reasonable way to view the possible risks and rewards is to say that the project will pay $50,000 with probability 0.2, will pay $100,000 with probability 0.3, w

> Compare the “probability of being within one standard deviation of the mean” for the exponential and normal distributions.