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intro stats

Questions and Answers of Intro Stats

Your supervisor asked you to fit many models to predict which customers will buy this holiday season. The firm is going to pick only one. What criteria would you recommend that the firm use to
Explain why boosting or other ways of averaging several models might be better than trying to find “the best.”SECTION 27.5
What are the pros and cons of combining multiple models to produce a prediction? Should we always combine models?
Is it a good idea to use the total accurate classification rate(percent of all cases properly classified) as the metric to evaluate the division’s models? Why or why not?SECTION 27.4
What are the advantages and disadvantages of using tree vs.neural network models?
Is any one portion of the CRISP-DM more important than the others? Why?SECTION 27.3
Your supervisor has read a couple of articles about data mining and artificial intelligence. He wants to use data mining to find the best customers. What would you suggest to structure this problem?
Your supervisor learned all about databases, and frequently makes queries such as: “What fraction of our customers who bought a product in the last six months are female and live within 5 miles of
Your supervisor is confused by Big Data. Explain what makes“big data” different than “data.”
Pottery An artist experimenting with clay to create pottery with a special texture has been experiencing difficulty with these special pieces. About 40% break in the kiln during firing.Hoping to
Did the player prove that he has improved?a) Suppose the player really is no better than before—still a 65% shooter. What’s the probability he can hit at least 9 of 10 shots anyway? (Hint: Use a
Hoops A basketball player with a poor foul-shot record practices intensively during the off-season. He tells the coach that he has raised his proficiency from 65% to 85%. Dubious, the coach asks him
Faulty or not? You are in charge of shipping computers to customers.You learn that a faulty chip was put into some of the machines. There’s a simple test you can perform, but it’s not perfect.
Two coins In a drawer are two coins. They look the same, but one coin produces heads 90% of the time when spun while the other one produces heads only 30% of the time. You select one of the coins.
Catheters, again The catheter company in Exercise 40 is reviewing its testing procedure.a) Suppose the significance level is changed to a = 0.01.Will the probability of a Type II error increase,
TV safety, revisited The manufacturer of the metal TV stands in Exercise 39 is thinking of revising its safety test.a) If the company’s lawyers are worried about being sued for selling an unsafe
Catheters During an angiogram, heart problems can be examined via a small tube (a catheter) threaded into the heart from a vein in the patient’s leg. It’s important that the company that
TV safety The manufacturer of a metal stand for home TV sets must be sure that its product will not fail under the weight of the TV. Since some larger sets weigh nearly 300 pounds, the company’s
Testing the ads The company in Exercise 36 contacts 620 people selected at random and only 157 remember the ad.a) Should the company renew the contract? Support your recommendation with an
They completed regular graded assignments and scored 72 points on the final with a standard deviation of 6.4 points.a) Should the professor invest time and effort on implementing the assignments
Motivating learning, part II 227 students signed up for the Stats course in Exercise
Ads A company is willing to renew its advertising contract with a city’s public transportation operator only if the operator can prove that more than 23% of the residents of the city have seen
Motivating learning A statistics professor has observed that, for several years, students score an average of 67 points out of 100 on the semester exam.A colleague suggested implementing regular
How would this affect the power of the test? Explain.
Stop signs Highway safety engineers test new road signs, hoping that increased reflectivity will make them more visible to drivers. Volunteers drive through a test course with several of the new- and
Equal opportunity? A company is sued for gender discrimination because only 41% of the newly hired candidates were women when 62% of all applicants were women. Is this strong evidence that the
Production Consider again the task of the quality control inspectors in Exercise 30.a) In this context, what is meant by the power of the test the inspectors conduct?b) They are currently testing 5
Cars, again As in Exercise 29, state regulators are checking up on repair shops to see if they are certifying vehicles that do not meet pollution standards.a) In this context, what is meant by the
Quality control Production managers on an assembly line must monitor the output to be sure that the level of defective products remains small. They periodically inspect a random sample of the items
Testing cars A clean air standard requires that vehicle exhaust emissions not exceed specified limits for various pollutants.Many states require that cars be tested annually to be sure they meet
Alzheimer’s Testing for Alzheimer’s disease can be a long and expensive process, consisting of lengthy tests and medical diagnosis. A group of researchers (Solomon et al., 1998) devised a
Homeowners 2018 According to recent data collected by Eurostat regarding homeownership rates across Europe, in 2018, 42.5% of people in Switzerland own their homes, the lowest rate in Europe. A study
When the points assigned to various components of an e-mail exceed the cutoff value you’ve set, the filter rejects its null hypothesis (that the message is real) and diverts that e-mail to a junk
More spam Consider again the points-based spam filter described in Exercise
Second loan Exercise 23 describes the loan score method a bank uses to decide which applicants it will lend money. Only if the total points awarded for various aspects of an applicant’s financial
Is that analogous to choosing a higher or lower value of a for a hypothesis test? Explain.d) What impact does this change in the cutoff value have on the chance of each type of error?
Spam Spam filters try to sort your e-mails, deciding which are real messages and which are unwanted. One method used is a point system. The filter reads each incoming e-mail and assigns points to the
Is that analogous to choosing a higher or lower value of a for a hypothesis test? Explain.d) What impact does this change in the cutoff value have on the chance of each type of error?
Loans Before lending someone money, banks must decide whether they believe the applicant will repay the loan. One strategy used is a point system. Loan officers assess information about the
Fans A survey of 92 randomly selected people standing in line to enter a tennis game at the Roland-Garros stadium found that 85 of them were fans of Rafael Nadal.a) Explain why we cannot use this
Dogs Canine hip dysplasia is a degenerative disease that causes pain in many dogs. Sometimes advanced warning signs appear in puppies as young as 6 months. A veterinarian checked 42 puppies whose
Hard times According to a study published by the Guardian in 2018, around 7.7% of workers will work at least two jobs to pay their bills.We assume this number was calculated based on a random sample
Mayor approval In April 2015, exactly one year after being elected Mayor of Paris, Anne Hidalgo’s approval rating stood at 53% according to a poll organized by IFOP for a French journal surveying
Is the euro fair? Soon after the euro was introduced as currency in Europe, it was widely reported that someone had spun a euro coin 250 times and gotten heads 140 times. We wish to test a hypothesis
Groceries A study conducted by the INSEE about the evolution of grocery shopping habits in France since 1974 shows that among some 5000 respondents (18 years+) surveyed in 2010, 2310 said they go
Alpha, again Environmentalists concerned about the impact of pesticides on human health found that there was no evidence of a higher rate of contamination among farmers using a new organic-based
Alpha A medical researcher testing new medication for dizziness has concluded that the new tested medicine is significantly more efficient than the current one. She made this decision based on a test
Another P-value Have harsher penalties and ad campaigns increased seatbelt use among drivers and passengers? Observations of commuter traffic failed to find evidence of a significant change compared
P-value A medical researcher tested a new treatment for poison ivy against the traditional ointment. He concluded that the new treatment is more effective. Explain what the P-value of 0.021 means in
More errors For each of the following situations, state whether a Type I, a Type II, or neither error has been made.a) A test of H0: m = 25 vs. HA: m 7 25 rejects the null hypothesis. Later it is
Errors For each of the following situations, state whether a Type I, a Type II, or neither error has been made. Explain briefly.a) A bank wants to know if the enrollment on their website is above 30%
Significant again? A new reading program may reduce the number of elementary school students who read below grade level. The company that developed this program supplied materials and teacher
Significant? Public health officials believe that 98% of children have been vaccinated against measles. A random survey of medical records at many schools across the country found that, among more
More critical values For each of the following situations, find the critical value for z or t.a) H0: m = 105 vs. HA: m • 105 at a = 0.05; n = 61.b) H0: p = 0.05 vs. HA: p 7 0.05 at a = 0.05.c) H0:
Critical values For each of the following situations, find the critical value(s) for z or t.a) H0: p = 0.5 vs. HA: p • 0.5 at a = 0.05.b) H0: p = 0.4 vs. HA: p 7 0.4 at a = 0.05.c) H0: m = 10 vs.
Alpha false and true Which of the following statements are true? If false, explain briefly.a) It is better to use an alpha level of 0.05 than an alpha level of 0.01.b) If we use an alpha level of
Alpha true and false Which of the following statements are true? If false, explain briefly.a) Using an alpha level of 0.05, a P-value of 0.04 results in rejecting the null hypothesis.b) The alpha
More P-values Which of the following are true? If false, explain briefly.a) A very low P-value provides evidence against the null hypothesis.b) A high P-value is strong evidence in favor of the null
P-values Which of the following are true? If false, explain briefly.a) A very high P-value is strong evidence that the null hypothesis is false.b) A very low P-value proves that the null hypothesis
False or true Which of the following are true? If false, explain briefly.a) If the null hypothesis is true, you’ll get a high P-value.b) If the null hypothesis is true, a P-value of 0.01 will occur
True or false Which of the following are true? If false, explain briefly.a) A P-value of 0.01 means that the null hypothesis is false.b) A P-value of 0.01 means that the null hypothesis has a 0.01
Chips Ahoy! again As we learned in Chapter 17, Exercise 59, in 1998, as an advertising campaign, the Nabisco Company announced a “1000 Chips Challenge,” claiming that every 18-ounce bag of their
More ski wax From Chapter 17, Exercise 58, Bjork Larsen was trying to decide whether to use a new racing wax for crosscountry skis. He decided that the wax would be worth the price if he could
More popcorn In Chapter 17, Exercise 57 we saw that Yvon Hopps ran an experiment to determine optimum power and time settings for microwave popcorn. His goal was to find a combination of power and
More Doritos We saw in Chapter 17, Exercise 56 that some students checked 6 bags of Doritos marked with a net weight of 28.3 grams. They carefully weighed the contents of each bag, recording the
More Ruffles Recall from Chapter 17, Exercise 55 that students investigated the packaging of potato chips. They purchased 6 bags of Lay’s Ruffles marked with a net weight of 28.3 grams. They
AP Stats 2016 The College Board reported that 60.3% of all students who took the 2016 AP Statistics exam earned scores of 3 or higher. One teacher wondered if the performance of her school was
John Wayne Like a lot of other Americans, John Wayne died of cancer. But is there more to this story? In 1955, Wayne was in Utah shooting the film The Conqueror. Across the state line, in Nevada, the
TV ads A start-up company is about to market a new computer printer. It decides to gamble by running commercials during the Super Bowl. The company hopes that name recognition will be worth the high
Lost luggage An airline’s public relations department says that the airline rarely loses passengers’ luggage. It further claims that on those occasions when luggage is lost, 90% is recovered and
Acid rain A study of the effects of acid rain on trees in a certain forest shows that 46 of 150 trees sampled exhibited some sort of damage from acid rain. This rate seemed to be higher than the 17%
Dropouts 2013 According to a report, the overall dropout average rate, which includes all students who do not complete upper secondary education, for a large country was around 15%. Subsequent
Jury Census data for a certain county show that 19% of the adult residents are Hispanic. Suppose 72 people are called for jury duty and only 9 of them are Hispanic. Does this apparent
Women executives A company is criticized because only 13 of 43 people in executive-level positions are women. The company explains that although this proportion is lower than it might wish, it’s
Seeds A garden center wants to store leftover packets of vegetable seeds for sale the following spring, but the center is concerned that the seeds may not germinate at the same rate a year later. The
WebZine A magazine is considering the launch of an online edition. The magazine plans to go ahead only if it’s convinced that more than 25% of current readers would subscribe. The magazine
Football 2016 During the first 15 weeks of the 2016 season, the home team won 137 of the 238 regular-season National Football League games. Is this strong evidence of a home field advantage in
Twins A national vital statistics report indicated that about 3%of all births produced twins. Is the rate of twin births the same among very young mothers? Data from a large city hospital found that
Scratch and dent An appliance manufacturer stockpiles washers and dryers in a large warehouse for shipment to retail stores.Sometimes in handling them the appliances get damaged. Even though the
Pollution A company with a fleet of 150 cars found that the emissions systems of 7 out of the 22 they tested failed to meet pollution control guidelines. Is this strong evidence that more than 20% of
Take the offer II We saw in Chapter 16, Exercise 36 that Top One tested the effectiveness of a double-miles campaign by recently sending out offers to a random sample of 100,000 cardholders. Of
Contributions, please II We learned in Chapter 16, Exercise 35 that the Care Association for the Blind recently sent letters to a random sample of 50,000 potential donors and received 2380 donations.
Educated mothers According to a Ministry of Education report for a large region, 42% of students reported that their mothers had graduated from college. In a survey conducted in a given year,
Absentees A certain Ministry of Education report states that 35% of students in a large region had not been absent from school even once during the previous month. In a survey conducted in a given
Candy Someone hands you a box of a dozen chocolate-covered candies, telling you that half are vanilla creams and the other half peanut butter. You pick candies at random and discover the first three
He cheats? A friend of yours claims that when he tosses a coin he can control the outcome. You are skeptical and want him to prove it. He tosses the coin, and you call heads; it’s tails.You try
Cars A survey investigating whether the proportion of today’s high school seniors who own their own cars is higher than it was a decade ago finds a P-value of 0.017. Is it reasonable to conclude
Relief A company’s old antacid formula provided relief for 70% of the people who used it. The company tests a new formula to see if it is better and gets a P-value of 0.27. Is it reasonable to
We don’t believe that claim, and roll the die 200 times to test an appropriate hypothesis. Our P-value turns out to be 0.03. Which conclusion is appropriate? Explain.a) There’s a 3% chance that
Dice The seller of a loaded die claims that it will favor the outcome
Negatives After the political ad campaign described in Exercise 15, parta, pollsters check the governor’s negatives.They test the hypothesis that the ads produced no change against the alternative
More hypotheses Write the null and alternative hypotheses you would use to test each situation.a) In the 1950s, only about 40% of high school graduates went on to college. Has the percentage
Hypotheses Write the null and alternative hypotheses you would use to test each of the following situations:a) A governor is concerned about his “negatives”—the percentage of state residents
Expensive medicine Developing a new drug can be an expensive process, resulting in high costs to patients. A pharmaceutical company has developed a new drug to reduce cholesterol, and it will conduct
Bad medicine Occasionally, a report comes out that a drug that cures some disease turns out to have a nasty side effect. For example, some antidepressant drugs may cause suicidal thoughts in younger
Golf balls The United States Golf Association (USGA) sets performance standards for golf balls. For example, the initial velocity of the ball may not exceed 250 feet per second when measured by an
Pizza A researcher tests whether the mean cholesterol level among those who eat frozen pizza exceeds the value considered to indicate a health risk. She gets a P-value of 0.07. Explain in this
Marriage In 1970, a European study indicated that the age at which women first married in Europe had a mean of 22.7 years.It is widely suspected that young people today are waiting longer to get
GRE performance again Instead of advertising the percentage of customers who improve by at least 10 points, a manager suggests testing whether the mean score improves at all. For each customer they
Seasonal rentals According to a recent study conducted by the Paris city hall, 7% of apartments in the first four districts are rented on a seasonal basis. The mayor of the 10th district wonders if

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