Question: At a barbershop music singing competition, choruses

> The data on water hardness and mortality considered in Part VI Review Exercise 30 also included information on whether the town is north or south of Derby. When that information is coded in a variable as 1 for north of Derby and 0 for south of Derby, and

> In an attempt to control the growth of the herds of wild horses, managers sterilized some of the stallions. The variable Sterilized is coded 0 for herds and years in which no stallions were sterilized and 1 for herds and years in which some stallions wer

> A student runs an experiment to test four different clubs on her putting accuracy, recording the distance in centimeters from a small target that she places on the green. She randomizes the club used each time by drawing numbers out of a hat until each c

> John Beale of Stanford, California, recorded the speeds of cars driving past his house, where the speed limit read 20 mph. The mean of 100 readings was 23.84 mph, with a standard deviation of 3.56 mph. (He actually recorded every car for a two-month peri

> Students in two basic Spanish classes were required to learn 50 new vocabulary words. One group of 45 students received the list on Monday and studied the words all week. Statistics summarizing this group scores on Friday quiz are given. The other group

> A student runs an experiment to test four different grips on his football throwing distance, recording the distance in yards that he can throw the football using each grip. He randomizes the grip used each time by drawing numbers out of a hat until each

> A weight loss clinic advertises that its program of diet and exercise will allow clients to lose 10 pounds in one month. A local reporter investigating weight reduction gets permission to interview a randomly selected sample of clients who report the giv

> Using the same survey as in Exercise 27, the student examined the relationship between Athletic Participation and Weight. Here are the boxplots of Weight by Athletic Participation: 1. State the null hypothesis about the students (both numerically and in

> Using a Simple Random Sample, a student asked 200 students questions about their study and workout habits, and received 124 responses. One of the questions asked, Do you participate in intramural (IM) athletics, varsity athletics, or no athletics? while

> The Los Angeles Almanac website reports recent annual rainfall (in inches), as shown in the table. 1. Create a 90% confidence interval for the mean annual rainfall in LA. 2. If you wanted to estimate the mean annual rainfall with a margin of error of onl

> Brianna, a member of the track team, runs an experiment to test how different factors affect her javelin throw. She wants to know if the more expensive (premium) javelin is worth the extra price and is curious to know how much warming up helps her distan

> A student runs an experiment to test how different factors affect his score while playing video pinball. Here are the results of 16 runs of an experiment performed in random order. Factor Eyes has two levels: both open and right eye closed. Factor Tilt h

> A study published in the journal Environmental Health Perspectives examined the sex ratios of children born to workers exposed to dioxin in Russian pesticide factories. The data covered the years 1961 to 1988 in the city of Ufa, Bashkortostan, Russia. Of

> Developers of a new math curriculum called Accelerated Math compared performances of students taught by their system with control groups of students in the same schools who were taught using traditional instructional methods and materials. Statistics abo

> Using N(1152,84), the Normal model for weights of Angus steers in Exercise 13 , 1. How many standard deviations from the mean would a steer weighing 1000 pounds be? 2. Which would be more unusual, a steer weighing 1000 pounds or one weighing 1250 pounds?

> The New York Times reported the results of the 2003 NY Marathon by listing time brackets and the number of racers who finished within that bracket. Because the brackets are of different sizes, we look at the number of racers finishing per minute against

> Nick (see Exercise 19) designed a follow-up experiment to see if having Music or Television on would affect his typing speed. In particular, he’d like to know if he can type just as effectively with the music and/or the TV on while he t

> How accurate are pollsters in predicting the outcomes of Congressional elections? The table shows the actual number of Democrat seats in the House of Representatives and the number predicted by the Gallup organization for nonpresidential election years s

> For a class project, Nick M. designed and carried out an experiment to see if the room Temperature and the wearing of Gloves affected his typing speed. He ran each combination of hot and cold temperature and gloves on and off 8 times, recording the net n

> The National Vital Statistics Report provides information on live Births (per 1000 women), according to the age of the woman (in 5-year brackets Age used here is the midpoint of the bracket) and the Year from 1990 to 1999. The report isolates births to w

> The Insurance Institute for Highway Safety publishes data on a variety of traffic related risks. One report gives the numbers of people killed in highway accidents during each year from 1975 to 2013. Here is a regression predicting Total traffic fataliti

> We have data on Old Faithful eruptions that includes another variable recording the Day on which the eruption occurred (where 1 is the first day and each successive day just counts one more). The correlation of Interval (minutes until the next eruption)

> The survey in Exercise 14 also asked students about the number of hours they studied. Those doing the survey wanted to know if the average amount of studying varied by sex or by class of the respondent. Partial boxplots of the Hours Studied last night by

> Using a Simple Random Sample, a student group asked 450 students about their sleep and study habits and received about 200 responses. The group wanted to know if the average amount of sleep varied by sex (F or M) or by year (Freshman, Sophomore, Junior,

> At a barbershop music singing competition, choruses are judged on three scales: Music (quality of the arrangement, etc.), Performance, and Singing. The scales are supposed to be independent of each other, and each is scored by a different judge, but a fr

> Two companies market new batteries targeted at owners of personal music players. DuraTunes claims a mean battery life of 11 hours, while RockReady advertises 12 hours. 1. Explain why you would also like to know the standard deviations of the battery life

> Here are data on 32 light water nuclear power plants. The variables are: Cost: In $100,000, adjusted to 1976 base. Date: Date that construction permit was issued in years after 1900. Thus, 68.58 is roughly halfway through 1968. Mwatts: Power plant net ca

> In preparation for a regional paper airplane competition, a student tried out her latest design. The distances her plane traveled (in feet) in 11 trial flights are given here. (The world record is an astounding 193.01 feet!) The data were 62, 52, 68, 23,

> In 2002 the Veritas Software company found out that its chief financial officer did not actually have the MBA he had listed on his resume. They fired him, and the value of the company stock dropped 19%. Kroll, Inc., a firm that specializes in investigati

> We have a sample of municipal mutual funds that report their return (%) in the previous 3years and the previous 5 years. 1. Create a 95% confidence interval for the difference in rate of return for the 3- and 5-year periods covered by these data. Clearly

> A corporation with a fleet of vehicles wanted to test the cost-effectiveness of using Motor Silk oil additive. For the study, 6100 delivery and passenger vehicles were tested for the same 3-month period in one year and then again in the subsequent year.

> A recent study of perfect pitch tested 2700 students in American music conservatories. It found that 7% of non-Asian and 32% of Asian students have perfect pitch. A test of the difference in proportions resulted in a P-value of

> Refer again to the research summarized in Exercise R6.6. Is there any evidence that when eclampsia does occur, the magnesium sulfide treatment may help prevent the woman death? 1. Write an appropriate hypothesis. 2. Check the assumptions and conditions.

> It estimated that 50,000 pregnant women worldwide die each year of eclampsia, a condition involving elevated blood pressure and seizures. A research team from 175 hospitals in 33 countries investigated the effectiveness of magnesium sulfate in preventing

> Who reads the newspaper more, men or women? Eurostat, an agency of the European Union (EU), conducts surveys on several aspects of daily life in EU countries. Recently, the agency asked samples of 1000 respondents in each of 14 European countries whether

> Fitting someone for a hearing aid requires assessing the patient hearing ability. In one method of assessment, the patient listens to a tape of 50 English words. The tape is played at low volume, and the patient is asked to repeat the words. The patient

> Anna, a language major, took final exams in both French and Spanish and scored 83 on each. Her roommate Megan, also taking both courses, scored 77 on the French exam and 95 on the Spanish exam. Overall, student scores on the French exam had a mean of 81

> Students in two basic Spanish classes were required to learn 50 new vocabulary words. One group of 45 students received the list on Monday and studied the words all week. Statistics summarizing this group scores on Friday quiz are given. The other group

> There is some indication in medical literature that doctors may have become more aggressive in inducing labor or doing preterm cesarean sections when a woman is carrying twins. Records at a large hospital show that, of the 43 sets of twins born in 2000,

> Thirteen overweight women volunteered for a study to determine whether eating specially prepared crackers before a meal could help them lose weight. The subjects were randomly assigned to eat crackers with different types of fiber (bran fiber, gum fiber,

> Peninsula Creameries sells both cottage cheese and ice cream. The CEO recently noticed that in months when the company sells more cottage cheese, it seems to sell more ice cream as well. Two of his aides were assigned to test whether this is true or not.

> According to an article in the Journal of Consulting and Clinical Psychology, Charles Borduin pioneered a treatment called Multisystemic Therapy (MST) as a way to prevent serious mental health problems in adolescents. The therapy involves a total support

> Developers of a new math curriculum called Accelerated Math compared performances of students taught by their system with control groups of students in the same schools who were taught using traditional instructional methods and materials. S

> Are good grades in high school associated with family togetherness? A Simple Random Sample of 142 high-school students was asked how many meals per week their families ate together. Their responses produced a mean of 3.78 meals per week, with a standard

> We saw in Part II Review Exercise R2.21 that Old Faithful eruptions do not occur at constant intervals and the intervals may vary greatly depending on the duration of the previous eruption. In that exercise, we fit a regression model, which we can now im

> Cereals with bran Exercise R6.41 looked at regressions to model calories in breakfast cereals based on their carbohydrates and fiber content. Here is a scatterplot of carbohydrates vs. fiber content for these cereals: The cereals plotted with green x are

> A 1954 study of 1438 pregnant women examined the association between the woman education level and the occurrence of unplanned pregnancies, producing these data: Do these data provide evidence of an association between family planning and education level

> The first Stat exam had a mean of 80 and a standard deviation of 4 points; the second had a mean of 70 and a standard deviation of 15 points. Reginald scored an 80 on the first test and an 85 on the second. Sara scored an 88 on the first but only a 65 on

> A regression of the calories in breakfast cereals on their carbohydrate content (g) looks like this: Response variable is: calories A second regression with fiber content included gives this model: Response variable is: calories 1. Give an interpretation

> At the middle of the 2016–2017 NBA season, James Hardin led the league by making 468 of 544 free throws, for a success rate of 86%. But Russell Westbook was close behind with 425 of 517 (82.2%). 1. Find a 95% confidence interval for the difference in t

> A survey of 1021 school-age children was conducted by randomly selecting children from several large urban elementary schools. Two of the questions concerned eye and hair color. In the survey, the following codes were used: The statistics students analyz

> The Pew Research Center conducted a representative telephone survey in October of 2016. Among the reported results was the following table concerning the preferred political party affiliation of respondents and their ages for white voters. Is there evide

> According to the 2011 Retirement Confidence Survey, run by the Employee Benefit Research Institute, 37% of men reported being a lot behind schedule while 43% of women answered in the same way. Is this evidence that in general, more women are feeling this

> Are twin births becoming more common? Part II Review Exercise R2.5 looked at the number of twin births by year from 1980 to 2014. Now we can include some inference: Response variable is: TwinBirths/1000 1. State and test the standard null hypothesis for

> In 2000, the Journal of the American Medical Association published a study that examined a sample of pregnancies that resulted in the birth of twins. Births were classified as preterm with intervention (induced labor or cesarean), preterm without such pr

> In 2016, about 200,000 statistics students nationwide took the Advanced Placement Examination in statistics. The national distribution of scores and the results at Ithaca High School are shown in the table. Is the distribution of scores at this high scho

> In an experiment to see if left- and right-handed people have different abilities in music, subjects heard a tone and were then asked to identify which of several other tones matched the first. Of 76 right-handed subjects, 38 were successful in completin

> The first Stats exam had a mean of 65 and a standard deviation of 10 points; the second had a mean of 80 and a standard deviation of 5 points. Derrick scored an 80 on both tests. Julie scored a 70 on the first test and a 90 on the second. They both total

> Large herds of wild horses can become a problem on some federal lands in the West. Researchers hoping to improve the management of these herds collected data to see if they could predict the number of foals that would be born based on the size of the cur

> The following table is based on a Gallup Poll of 1015 U.S. adults on April 912, 2015. Respondents were classified as high income (over $75,000), middle income ($30k $75k), or low income (less than $30k). Those polled were asked for their views on redist

> In an investigation of environmental causes of disease, data were collected on the annual mortality rate (deaths per 100,000) for males in 61 large towns in England and Wales. In addition, the water hardness was recorded as the calcium concentration (par

> Joseph Lister (for whom Listerine is named!) was a British physician who was interested in the role of bacteria in human infections. He suspected that germs were involved in transmitting infection, so he tried using carbolic acid as an operating room dis

> Nambe Mills manufactures plates, bowls, and other tableware made from an alloy of several metals. Each item must go through several steps, including polishing. To better understand the production process and its impact on pricing, the company checked the

> Two human traits controlled by a single gene are the ability to roll one tongue and whether one ear lobes are free or attached to the neck. Genetic theory says that people will have neither, one, or both of these traits in the ratio 1:3:3:9 (1 attached,

> 1. Make histograms of the cloud seeding data for both unseeded and seeded clouds. Do you think either of the inference methods used in Exercise R6.26 is appropriate? 2. Find a re-expression that improves the distributions of the cloud seeding rainfall am

> In an experiment to determine whether seeding clouds with silver iodide increases rainfall, 52 clouds were randomly assigned to be seeded or not. The amount of rain they generated was then measured (in acre-feet). a. Create a 95% confidence interval for

> A study published in the Journal of the American Medical Association examined people to see if they showed any signs of IRS (insulin resistance syndrome) involving major risk factors for Type 2 diabetes and heart disease. Among 102 subjects who consumed

> In 1936 Sir Ronald Fisher presented data on irises as the example in a famous statistics paper. Ever since, Fisher Iris data have been a feature of statistics texts. We didn’t want to be an exception. Can measurements of the petal lengt

> In the last chapter, we looked we look at three outliers arising from a plot of Average Wind Speed by Month in the Hopkins Forest. Each was is associated with an unusually strong storm, but which was is the most remarkable for its month? Here are the sum

> The study described in Exercise R6.21 also looked at scores in mathematics and language. Here are software outputs for the appropriate tests. Explain what they show. Mathematics T-TEST OF Mu(1) Mu(2)=0Mu(Cert) Mu(NoCert)=4.53t(86)=2.95p=0.002 Language T

> In 1974, the Bellevue-Stratford Hotel in Philadelphia was the scene of an outbreak of what later became known as Legionnaires disease. The cause of the disease was finally discovered to be bacteria that thrived in the air-conditioning units of the hotel.

> Several programs attempt to address the shortage of qualified teachers by placing uncertified instructors in schools with acute needs often in inner cities. A study compared students taught by certified teachers to others taught by uncertified teachers i

> Some people fear that differences in insurance coverage can affect health care decisions. A survey of several randomly selected hospitals found that 16.6% of 223 recent births in Vermont involved cesarean deliveries, compared to 18.8% of 186 births in Ne

> During a 2-month period, 72 babies were born at the Tompkins Community Hospital in upstate New York. The table shows how many babies were born on each day of the week. 1. If births are uniformly distributed across all days of the week, how many would you

> A study conducted in the multicultural Spanish city of Ceuta investigated the relationship between religion and the prevalence of eating disorders. Students aged 12-20 were selected from three public schools. In the study, suppose there were 150 Muslim s

> In the depression and heart attack research described in Exercise R6.17, 32% of the diseased group were smokers, compared with only 23.7% of those free of heart disease. 1. Create a 95% confidence interval for the difference in the proportions of smokers

> In a study of how depression may affect one ability to survive a heart attack, the researchers reported the ages of the two groups they examined. The mean age of 2397 patients without cardiac disease was 69.8 years (SD=8.7Â years), while for the 450 pati

> The National Highway Traffic Safety Administration reported seat belt use and fatalities in car accidents. (Seat belt use in 2015 use rates in the states and territories. Report no. DOT HS-812-274) Is the rate of seat belt use different in New England co

> In the midwestern United States, a large aquaculture industry raises largemouth bass. Researchers wanted to know whether the fish would grow better if fed a natural diet of fathead minnows or an artificial diet of food pellets. They stocked six ponds wit

> Corey has 4929 songs in his computer music library. The songs have a mean duration of 242.4 seconds with a standard deviation of 114.51 seconds. On the Nickel, by Tom Waits, is 380 seconds long. What is its z-score?

> Does race matter when applying for National Institutes of Health grants? A study found that of 58,148 applications submitted by white researchers, 15,700 were accepted and funded by the NIH. Additionally, 198 of the 1164 applications submitted by black r

> Archaeologists can use the chemical composition of clay found in pottery artifacts to determine whether different sites were populated by the same ancient people. They collected five samples of Romano-British pottery from each of two sites in Great Brita

> Can pleasant smells improve learning? Researchers timed 21 subjects as they tried to complete paper-and-pencil mazes. Each subject attempted a maze both with and without the presence of a floral aroma. Subjects were randomized with respect to whether the

> A study found that babies born at different times of the year may develop the ability to crawl at different ages. The authors of the study suggested that these differences may be related to the temperature at the time the infant is 6 months old. (Benson

> Among 242 Cleveland-area children born prematurely at low birthweights between 1977 and 1979, only 74% graduated from high school. Among a comparison group of 233 children of normal birthweight, 83% were high school graduates. (Outcomes in Young Adulthoo

> A report in the New England Journal of Medicine notes growing evidence that the herb Aristolochia fangchi can cause urinary tract cancer in those who take it. Suppose you are asked to design an experiment to study this claim. Imagine that you have data o

> In June 2017, Pew Research asked a random sample of 2504 U.S. adults, Do you strongly favor, favor, oppose, or strongly oppose allowing gays and lesbians to marry legally? (www.people-press.org/2017/06/26/support-for-same-sex-marriage-grows-even-among-g

> We are sampling randomly from a distribution known to be bimodal. 1. As our sample size increases, what the expected shape of the sample distribution? 2. What the expected value of our sample mean? Does the size of the sample matter? 3. How is the variab

> Using a computer to play many simulated games of Scrabble, researcher Charles Robinove found that the letter A occurred in 54% of the hands. This study had a margin of error of ±10% (Chance, 15, no. 1 [2002]) 1. Explain what the margin of error means in

> In a survey of 1002 U.S. adults in December 2016 by Pew Research (www.journalism.org/2016/12/15/many-americans-believe-fake-news-is-sowing-confusion/), 64% of adult respondents say they think that made-up news is causing a great deal of confusion about t

> A high school senior uses the Internet to get information on February temperatures in the town where he’ll be going to college. He finds a website with some statistics, but they are given in degrees Celsius. The conversion formula is F=9/5 C+32. Determin

> The fastest horse in Kentucky Derby history was Secretariat in 1973. The scatterplot shows speed (in miles per hour) of the winning horses each year. What do you see? In most sporting events, performances have improved and continue to improve, so surely

> The 2016 U.S. presidential election was unusual in several ways. First, the candidate who won the most electoral votes, Donald Trump, did not win the most popular votes. Second, several minor-party candidates received enough votes to possibly affect the

> In a car rental company fleet, 70% of the cars are American brands, 20% are Japanese, and the rest are German. The company notes that manufacturers recalls seem to affect 2% of the American cars, but only 1% of the others. 1. What the probability that a

> How large are hamster litters? Among 47 golden hamster litters recorded, there were an average of 7.72 baby hamsters, with a standard deviation of 2.5 hamsters per litter. 1. Create and interpret a 90% confidence interval. 2. Would a 98% confidence inter

> We work for the Watchdog for the Consumer consumer advocacy group. We’ve been asked to look at a battery company that claims its batteries last an average of 100 hours under normal use. There have been several complaints that the batteries don’t last tha

> Every statement about a confidence interval contains two parts the level of confidence and the interval. Suppose that an insurance agent estimating the mean loss claimed by clients after home burglaries created the 95% confidence interval ($1644, $2391).

> As a project for an Introductory Statistics course, students checked 6 bags of Fritos marked with a net weight of 35.4 grams. They carefully weighed the contents of each bag, recording the following weights (in grams): 35.5, 35.3, 35.1, 36.4, 35.4, 35.5.

> Clarksburg Bakery is trying to predict how many loaves to bake. In the past 100 days, the bakery has sold between 95 and 140 loaves per day. Here are a histogram and the summary statistics for the number of loaves sold for the past 100 days. 1. Can you u

> In February 2012, MedPage Today reported that researchers used vemurafenib to treat metastatic melanoma (skin cancer). Out of 152 patients, 53% had a partial or complete response to vemurafenib. 1. Write a 95% confidence interval for the proportion helpe