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business
business statistics in practice

Questions and Answers of Business Statistics In Practice

Perform a significance test to compare two proportions.
How can we find formulas for the mean and standard deviation of the sampling distribution of p^ 1− p^ 2?
Goldfish Refer to the example on page 615. Suppose that your teacher decides to take SRSs of 100 crackers from both bags instead.(a) What is the shape of the sampling distribution of p^1− p^2?
Homework Refer to page 612. Suppose that both school counselors decide to take SRSs of 150 students instead.(a) What is the shape of the sampling distribution of p^1− p^2? Why?(b) Find the mean of
I want red! A candy maker offers Child and Adult bags of jelly beans with different color mixes. The company claims that the Child mix has 30% red jelly beans, while the Adult mix contains 15% red
Literacy A researcher reports that 80% of high school graduates, but only 40% of high school dropouts, would pass a basic literacy test.5 Assume that the researcher’s claim is true. Suppose we give
Don’t drink the water! The movie A Civil Action(Touchstone Pictures, 1998) tells the story of a major legal battle that took place in the small town of Woburn, Massachusetts. A town well that
In-line skaters A study of injuries to in-line skaters used data from the National Electronic Injury Surveillance System, which collects data from a random sample of hospital emergency rooms. The
Shrubs and fire Fire is a serious threat to shrubs in dry climates. Some shrubs can resprout from their roots after their tops are destroyed. One study of resprouting took place in a dry area of
Broken crackers We don’t like to find broken crackers when we open the package. How can makers reduce breaking? One idea is to microwave the crackers for 30 seconds right after baking them. Breaks
Who tweets? Do younger people use Twitter more often than older people? In a random sample of 316 adult Internet users aged 18 to 29, 26% used Twitter.In a separate random sample of 532 adult
Listening to rap Is rap music more popular among young blacks than among young whites?A sample survey compared 634 randomly chosen blacks aged 15 to 25 with 567 randomly selected whites in the same
Young adults living at home A surprising number of young adults (ages 19 to 25) still live in their parents’homes. A random sample by the National Institutes of Health included 2253 men and 2629
Fear of crime The elderly fear crime more than younger people, even though they are less likely to be victims of crime. One study recruited separate random samples of 56 black women and 63 black men
Who owns iPods? As part of the Pew Internet and American Life Project, researchers surveyed a random sample of 800 teens and a separate random sample of 400 young adults. For the teens, 79% said that
Steroids in high school A study by the National Athletic Trainers Association surveyed random samples of 1679 high school freshmen and 1366 high school seniors in Illinois. Results showed that 34 of
Who owns iPods? Refer to Exercise 13. Carry out a significance test at the a = 0.05 level.
Steroids in high school Refer to Exercise 14. Carry out a significance test at the a = 0.05 level.
Who owns iPods? Refer to Exercise 13. Construct and interpret a 95% confidence interval for the difference between the population proportions. Explain how the confidence interval is consistent with
Steroids in high school Refer to Exercise 14. Construct and interpret a 95% confidence interval for the difference between the population proportions.Explain how the confidence interval is consistent
Children make choices Many new products introduced into the market are targeted toward children.The choice behavior of children with regard to new products is of particular interest to companies that
Marriage and status “Would you marry a person from a lower social class than your own?” Researchers asked this question of a random sample of 385 black, never-married college students. Of the 149
Driving school A driving school owner believes that Instructor A is more effective than Instructor B at preparing students to pass the state’s driver’s license exam. An incoming class of 100
Preventing strokes Aspirin prevents blood from clotting and so helps prevent strokes. The Second European Stroke Prevention Study asked whether adding another anticlotting drug, named dipyridamole,
Prayer and pregnancy Two hundred women who were about to undergo IVF served as subjects in an experiment. Each subject was randomly assigned to either a treatment group or a control group.Women in
Acupuncture and pregnancy A study reported in the medical journal Fertility and Sterility sought to determine whether the ancient Chinese art of acupuncture could help infertile women become
Take pM and pF to be the proportions of all college males and females who worked last summer. The hypotheses to be tested are(a) H0: pM − pF = 0 versus Ha: pM − pF ≠ 0.(b) H0: pM − pF = 0
The researchers report that the results were statistically significant at the 1% level. Which of the following is the most appropriate conclusion?(a) Because the P-value is less than 1%, fail to
Which of the following is the correct margin of error for a 99% confidence interval for the difference in the proportion of male and female college students who worked for pay last summer?(a)
In an experiment to learn whether Substance M can help restore memory, the brains of 20 rats were treated to damage their memories. First, the rats were trained to run a maze. After a day, 10
Drive my car (3.2)(a) What is the equation of the least-squares regression line? Be sure to define any symbols you use.(b) Interpret the slope of the least-squares line in the context of this
Drive my car (3.2, 4.3)(a) Explain what the value of r2 tells you about how well the least-squares line fits the data.(b) The mean age of the students’ cars in the sample was x– = 8 years. Find
Describe the shape, center, and spread of the sampling distribution of x–1 − x–2.
Determine whether the conditions are met for doing inference about m1 − m2.
Construct and interpret a confidence interval to compare two means.
Perform a significance test to compare two means.
Determine when it is appropriate to use two-sample t procedures versus paired t procedures.
Does Polyester Decay?
Cholesterol The level of cholesterol in the blood for all men aged 20 to 34 follows a Normal distribution with mean 188 milligrams per deciliter (mg/dl) and standard deviation 41 mg/dl. For
How tall? The heights of young men follow a Normal distribution with mean 69.3 inches and standard deviation 2.8 inches. The heights of young women follow a Normal distribution with mean 64.5 inches
Shoes How many pairs of shoes do teenagers have?To find out, a group of AP® Statistics students conducted a survey. They selected a random sample of 20 female students and a separate random sample
Household size How do the numbers of people living in households in the United Kingdom (U.K.) and South Africa compare? To help answer this question, we used CensusAtSchool’s random data selector
Literacy rates Do males have higher average literacy rates than females in Islamic countries? The table below shows the percent of men and women who were literate in the major Islamic nations at the
Long words Mary was interested in comparing the mean word length in articles from a medical journal and an airline’s in-flight magazine. She counted the number of letters in the first 400 words of
Is red wine better than white wine? Observational studies suggest that moderate use of alcohol by adults reduces heart attacks and that red wine may have special benefits. One reason may be that red
Tropical flowers Different varieties of the tropical flower Heliconia are fertilized by different species of hummingbirds.Researchers believe that over time, the lengths of the flowers and the forms
Paying for college College financial aid offices expect students to use summer earnings to help pay for college. But how large are these earnings? One large university studied this question by asking
Happy customers As the Hispanic population in the United States has grown, businesses have tried to understand what Hispanics like. One study interviewed a random sample of customers leaving a bank.
Baby birds Do birds learn to time their breeding?Blue titmice eat caterpillars. The birds would like lots of caterpillars around when they have young to feed, but they must breed much earlier. Do the
DDT in rats Poisoning by the pesticide DDT causes convulsions in humans and other mammals.Researchers seek to understand how the convulsions are caused. In a randomized comparative experiment, they
Who talks more—men or women? Researchers equipped random samples of 56 male and 56 female students from a large university with a small device that secretly records sound for a random 30 seconds
Competitive rowers What aspects of rowing technique distinguish between novice and skilled competitive rowers? Researchers compared two randomly selected groups of female competitive rowers: a group
Teaching reading An educator believes that new reading activities in the classroom will help elementary school pupils improve their reading ability. She recruits 44 third-grade students and randomly
Does breast-feeding weaken bones? Breast-feeding mothers secrete calcium into their milk. Some of the calcium may come from their bones, so mothers may lose bone mineral. Researchers compared a
Who talks more—men or women? Refer to Exercise 43. Construct and interpret a 95% confidence interval for the difference in mean number of words spoken in a day. Explain how this interval provides
DDT in rats Refer to Exercise 42. Construct and interpret a 95% confidence interval for the difference in mean relative height of the second spike’s electrical response. Explain how this interval
A better drug? In a pilot study, a company’s new cholesterol-reducing drug outperforms the currently available drug. If the data provide convincing evidence that the mean cholesterol reduction with
Down the toilet A company that makes hotel toilets claims that its new pressure-assisted toilet reduces the average amount of water used by more than 0.5 gallon per flush when compared to its current
Rewards and creativity Dr. Teresa Amabile conducted a study involving 47 college students who were randomly assigned to two treatment groups.The 23 students in one group were given a list of
Sleep deprivation Does sleep deprivation linger for more than a day? Researchers designed a study using 21 volunteer subjects between the ages of 18 and 25. All 21 participants took a computer-based
Paired or unpaired? In each of the following settings, decide whether you should use paired t procedures or two-sample t procedures to perform inference. Explain your choice.39(a) To test the wear
Paired or unpaired? In each of the following settings, decide whether you should use paired t procedures or two-sample t procedures to perform inference. Explain your choice.40(a) To compare the
Coaching and SAT scores Let’s first ask if students who are coached increased their scores significantly.(a) You could use the information on the Coached line to carry out either a two-sample t
Coaching and SAT scores What we really want to know is whether coached students improve more than uncoached students, and whether any advantage is large enough to be worth paying for. Use the
There are two common methods for measuring the concentration of a pollutant in fish tissue. Do the two methods differ, on average? You apply both methods to each fish in a random sample of 18 carp
Which of the following describes a Type II error in the context of this study?(a) Finding convincing evidence that the true means are different for males and females, when in reality the true means
The P-value for the stated hypotheses is 0.002. Interpret this value in the context of this study.(a) Assuming that the true mean road rage score is the same for males and females, there is a 0.002
Based on the P-value in Exercise 59, which of the following must be true?(a) A 90% confidence interval for mM − mF will contain 0.(b) A 95% confidence interval for mM − mF will contain 0.(c) A
Which inference method?(a) Drowning in bathtubs is a major cause of death in children less than 5 years old. A random sample of parents was asked many questions related to bathtub safety. Overall,
Which inference method?(a) How do young adults look back on adolescent romance?Investigators interviewed 40 couples in their midtwenties. The female and male partners were interviewed separately.
Quality control (2.2, 5.3, 6.3) Many manufacturing companies use statistical techniques to ensure that the products they make meet standards. One common way to do this is to take a random sample of
Information online (8.2, 10.1) A random digit dialing sample of 2092 adults found that 1318 used the Internet.42 Of the users, 1041 said that they expect businesses to have Web sites that give
Coaching and SAT scores: Critique (4.1, 4.3) The data in Exercises 55 and 56 came from a random sample of students who took the SAT twice. The response rate was 63%, which is fairly good for
Which procedure? For each of the following settings, say which inference procedure from Chapter 8, 9, or 10 you would use. Be specific. For example, you might say, “Two-sample z test for the
Seat belt use The proportion of drivers who use seat belts depends on things like age (young people are more likely to go unbelted) and gender (women are more likely to use belts). It also depends on
Expensive ads Consumers who think a product’s advertising is expensive often also think the product must be of high quality. Can other information undermine this effect? To find out, marketing
Men versus women The National Assessment of Educational Progress (NAEP) Young Adult Literacy Assessment Survey interviewed a random sample of 1917 people 21 to 25 years old. The sample contained 840
Treating AIDS The drug AZT was the first drug that seemed effective in delaying the onset of AIDS. Evidence for AZT’s effectiveness came from a large randomized comparative experiment.The subjects
Conditions Explain why it is not safe to use the methods of this chapter to perform inference in each of the following settings.(a) Lyme disease is spread in the northeastern United States by
Each day I am getting better in math A “subliminal”message is below our threshold of awareness but may nonetheless influence us. Can subliminal messages help students learn math? A group of 18
A study of road rage asked separate random samples of 596 men and 523 women about their behavior while driving. Based on their answers, each respondent was assigned a road rage score on a scale of 0
Thirty-five people from a random sample of 125 workers from Company A admitted to using sick leave when they weren’t really ill. Seventeen employees from a random sample of 68 workers from Company
The power takeoff driveline on tractors used in agriculture is a potentially serious hazard to operators of farm equipment. The driveline is covered by a shield in new tractors, but for a variety of
A quiz question gives random samples of n = 10 observations from each of two Normally distributed populations. Tom uses a table of t distribution critical values and 9 degrees of freedom to calculate
The correct test statistic is(a) z =(6 − 5) − 0Å3 60+2 40(b) z =(6 − 5) − 0Å32 60+22 40(c) t =(6 − 5) − 0 3"60+2"40(d) t =(6 − 5) − 0Å3 60+2 40(e) t =(6 − 5) − 0Å32 60+22 40
The P-value for the test is 0.048. A correct conclusion is to(a) fail to reject H0 at the a = 0.05 level. There is convincing evidence of a difference in the average time spent on extracurricular
At a baseball game, 42 of 65 randomly selected people own an iPod. At a rock concert occurring at the same time across town, 34 of 52 randomly selected people own an iPod. A researcher wants to test
An SRS of size 100 is taken from Population A with proportion 0.8 of successes. An independent SRS of size 400 is taken from Population B with proportion 0.5 of successes. The sampling distribution
How much more effective is exercise and drug treatment than drug treatment alone at reducing the rate of heart attacks among men aged 65 and older? To find out, researchers perform a completely
Researchers are interested in evaluating the effect of a natural product on reducing blood pressure.This will be done by comparing the mean reduction in blood pressure of a treatment (natural
Researchers wondered whether maintaining a patient’s body temperature close to normal by heating the patient during surgery would affect wound infection rates. Patients were assigned at random to
A random sample of 100 of a certain popular car model last year found that 20 had a certain minor defect in the brakes. The car company made an adjustment in the production process to try to reduce
Pat wants to compare the cost of one- and twobedroom apartments in the area of her college campus. She collects data for a random sample of 10 advertisements of each type. The table below shows the
Suppose the probability that a softball player gets a hit in any single at-bat is 0.300. Assuming that her chance of getting a hit on a particular time at bat is independent of her other times at
The probability that Color Me Dandy wins a horse race at Batavia Downs given good track conditions is 0.60. The probability of good track conditions on any given day is 0.85. What is the probability
Sports Illustrated planned to ask a random sample of Division I college athletes, “Do you believe performance-enhancing drugs are a problem in college sports?” How many athletes must be
The distribution of grade point averages for a certain college is approximately Normal with a mean of 2.5 and a standard deviation of 0.6. Within which of the following intervals would we expect to
Which of the following will increase the power of a significance test?(a) Increase the Type II error probability.(b) Decrease the sample size.(c) Reject the null hypothesis only if the P-value is
You can find some interesting polls online. Anyone can become part of the sample just by clicking on a response. One such poll asked, “Do you prefer watching first-run movies at a movie theater, or
A certain candy has different wrappers for various holidays. During Holiday 1, the candy wrappers are 30% silver, 30% red, and 40% pink. During Holiday 2, the wrappers are 50% silver and 50% blue.

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