Questions and Answers of Practice of Statistics

Do drivers take longer to leave their parking spaces when someone is waiting? Researchers hung out in a parking lot and collected some data. The graphs and numerical summaries display information
To find out what proportion of Americans support proposed Medicare legislation to help pay medical costs, the AARP conducted a survey of their members (people over age 50 who pay membership dues).
Ten percent of U.S. households contain 5 or more people. You want to simulate choosing a household at random and recording “Yes” if it contains 5 or more people. Which of these is a correct
Suppose this player attempts 10 shots in a game and makes only 3 of them. Does this provide convincing evidence that she is less than a 47% shooter?a. Yes, because 3/10 (30%) is less than 47%.b. Yes,
A total of 25 repetitions of the simulation were performed. The number of makes in each set of 10 simulated shots was recorded on the dotplot. What is the approximate probability that a 47% shooter
If I toss a fair coin five times and the outcomes are TTTTT, then the probability that tails appears on the next toss isa. 0.5.b. less than 0.5.c. greater than 0.5.d. 0.e. 1.Select the best answer.
To simulate the number of makes in 10 shot attempts, you would perform the simulation as follows:a. Use 10 random one-digit numbers, where 0–4 are a make and 5– 9 are a miss.b. Use 10 random
A recent study reported that fewer than half of young adults turn off the water while brushing their teeth. Is the same true for teenagers? To find out, a group of statistics students asked an SRS of
You read in a book about bridge that the probability that each of the four players is dealt exactly one ace is approximately 0.11. This means thata. in every 100 bridge deals, each player has 1 ace
About 7% of men in the United States have some form of red–green color blindness. Suppose we randomly select one U.S. adult male at a time until we find one who is red–green colorblind. Should we
Do most teens recycle? To find out, an AP® Statistics class asked an SRS of 100 students at their school whether they regularly recycle. In the sample, 55 students said that they recycle. Is this
Every 9 weeks, Mr. Millar collects students’ notebooks and checks their homework. He randomly selects 4 different assignments to inspect for all of the students. Marino is one of the students in
A website claims that 10% of U.S. adults are left-handed. A researcher believes that this figure is too low. She decides to test this claim by taking a random sample of 20 U.S. adults and recording
According to New Jersey Transit, the 8:00 A.M. weekday train from Princeton to New York City has a 90% chance of arriving on time. To test this claim, an auditor chooses 6 weekdays at random during a
Researchers recruited 20 volunteers—8 men and 12 women—to take part in an experiment. They randomly assigned the subjects into two groups of 10 people each. To their surprise, 6 of the 8 men were
In the game of Scrabble, each player begins by randomly selecting 7 tiles from a bag containing 100 tiles. There are 42 vowels, 56 consonants, and 2 blank tiles in the bag. Cait chooses her 7 tiles
A media report claims that 50% of U.S. teens with smartphones feel addicted to their devices.3 A skeptical researcher believes that this figure is too high. She decides to test the claim by taking a
At the end of basketball practice, each player on the team must shoot free throws until he makes 10 of them. Dwayne is a 70% free-throw shooter. That is, his probability of making any free throw is
The Transportation Security Administration (TSA) is responsible for airport safety. On some flights, TSA officers randomly select passengers for an extra security check prior to boarding. One such
A professional tennis player claims to get 90% of her second serves in. In a recent match, the player missed 5 of her first 20 second serves. Is this a surprising result if the player’s claim is
Luke’s teacher has assigned each student in his class an online quiz, which is made up of 10 multiple-choice questions with 4 options each. Luke hasn’t been paying attention in class and has to
A very good professional baseball player gets a hit about 35% of the time over an entire season. After the player failed to hit safely in six straight at-bats, a TV commentator said, “He is due for
a. A gambler knows that red and black are equally likely to occur on each spin of a roulette wheel. He observes that 5 consecutive reds have occurred and bets heavily on black at the next spin. Asked
The figure shows the results of two different sets of 5000 coin tosses. Explain what this graph tells you about chance behavior in the short run and the long run. 1.0 0.9 - 0.8 - 0.7 - 0.6 - 0.5 0.4
The figure shows the results of a basketball player attempting many 3 point shots. Explain what this graph tells you about chance behavior in the short run and long run. 100 50 1000 Number of shots
Many women choose to have annual mammograms to screen for breast cancer after age 40. A mammogram isn’t foolproof. Sometimes the test suggests that a woman has breast cancer when she really
Sometimes police use a lie detector test to help determine whether a suspect is telling the truth. A lie detector test isn’t foolproof sometimes it suggests that a person is lying when he or she is
There are many married couples in which the husband and wife both carry a gene for cystic fibrosis but don’t have the disease themselves. Suppose we select one of these couples at random. According
If Aaron tunes into his favorite radio station at a randomly selected time, there is a 0.20 probability that a commercial will be playing.a. Interpret this probability as a long-run relative
The business magazine Forbes reports that 4567 companies sold their first stock to the public between 1990 and 2000. The mean change in the stock price of these companies since the first stock was
“It is right to use animals for medical testing if it might save human lives.” The General Social Survey asked 1152 adults to react to this statement. Here is the two-way table of their
Do product labels influence customer perceptions? To find out, researchers recruited more than 500 adults and asked them to estimate the number of calories, amount of added sugar, and amount of fat
Some news organizations maintain a database of customers who have volunteered to share their opinions on a variety of issues. Suppose that one of these databases includes 9000 registered voters in
Researchers on aging proposed to investigate the effect of supplemental health services on the quality of life of older people. Eligible patients on the rolls of a large medical clinic were to be
Texas A&M, like many universities, offers screening for HIV, the virus that causes AIDS. Students may choose either anonymous or confidential screening. An announcement says, “Persons who sign
In the 1960s, children entering the Willowbrook State School, an institution for the intellectually disabled on Staten Island in New York, were deliberately infected with hepatitis. The researchers
One of the most important nongovernment surveys in the United States is the National Opinion Research Center’s General Social Survey (GSS). The GSS regularly monitors public opinion on a wide
In which of the circumstances listed here would you allow collecting personal information without the subjects’ consent?a. A government agency takes a random sample of income tax returns to obtain
In cooperation with researchers from Cornell University, Facebook randomly selected almost 700,000 users for an experiment in “emotional contagion.” Users’ news feeds were manipulated (without
Government regulations require that institutional review boards consist of at least five people, including at least one scientist, one nonscientist, and one person from outside the institution. Most
You have been invited to serve on a college’s institutional review board. You must decide whether several research proposals qualify for lighter review because they involve only minimal risk to
A study of strength training and memory randomly assigned 46 young adults to two groups. After both groups were shown 90 pictures, one group had to bend and extend one leg against heavy resistance 60
Eating blueberries and strawberries might improve heart health, according to a long-term study of 93,600 women who volunteered to take part. These berries are high in anthocyanins due to their
Is a friendly surgeon a better surgeon? In a study of more than 32,000 surgical patients from 7 different medical centers, researchers classified surgeons by the number of unsolicited complaints that
One of the better studies of the effect of regular attendance at religious services gathered data from a random sample of 3617 adults. The researchers then measured lots of variables, not just the
Will storing batteries in a freezer make them last longer? To find out, a company that produces batteries takes a random sample of 100 AA batteries from its warehouse. The company statistician
Do abandoned children placed in foster homes do better than similar children placed in an institution? The Bucharest Early Intervention Project found statistically significant evidence that they do.
A study published in the New England Journal of Medicine compared two medicines to treat head lice: an oral medication called ivermectin and a topical lotion containing malathion. Researchers studied
Dr. Linda Stern and her colleagues recruited 132 obese adults at the Philadelphia Veterans Affairs Medical Center in Pennsylvania. Half the participants were randomly assigned to a low-carbohydrate
Are people influenced by what others say? Michael conducted an experiment in front of a popular gym. As people entered, he asked them how many days they typically work out per week. As he asked the
Over the years, the percentage of births that are planned caesarean sections has been rising. Because doctors can schedule these deliveries, there might be more children born during the week and
According to a newspaper article, “Most people are kissing the ‘right way.’” That is, according to a study, the majority of couples prefer to tilt their heads to the right when kissing. In
Using a webcam, a traffic analyst selected a random sample of 800 cars traveling on I-195 in Miami on a weekday morning. Among the 800 cars in the sample, 24% were white. The margin of error for this
A Gallup poll conducted telephone interviews with a random sample of 1000 adults aged 18 and older. Of these, 37% said that football is their favorite sport to watch on television. The margin of
What proportion of students at your school use Twitter? To find out, you survey a simple random sample of students from the school roster.a. Will your sample result be exactly the same as the true
The boxplots summarize the distributions of average monthly rainfall (in inches) for Tucson, Arizona, and Princeton, New Jersey.52 Compare these distributions. Princeton - Tucson -E 1 2 3 4 5 Average
A researcher wants to estimate the average distance that students at a large community college live from campus. To find out, she surveys a simple random sample of students from the registrar’s
Biological measurements on the same species often follow a Normal distribution quite closely. The weights of seeds of a variety of winged bean are approximately Normal with mean 525 milligrams (mg)
Two essential features of all statistically designed experiments area. Comparing several treatments; using the double-blind method.b. Comparing several treatments; using chance to assign subjects to
A report in a medical journal notes that the risk of developing Alzheimer’s disease among subjects who regularly opted to take the drug ibuprofen was about half the risk of those who did not. Is
A farmer is conducting an experiment to determine which variety of apple tree, Fuji or Gala, will produce more fruit in his orchard. The orchard is divided into 20 equally sized square plots. He has
Corn variety 1 yielded 140 bushels per acre last year at a research farm. This year, corn variety 2, planted in the same location, yielded only 110 bushels per acre. Based on these results, is it
A gardener wants to try different combinations of fertilizer (none, 1 cup, 2 cups) and mulch (none, wood chips, pine needles, plastic) to determine which combination produces the highest yield for a
To investigate if standing up while studying affects performance in an algebra class, a teacher assigns half of the 30 students in his class to stand up while studying and assigns the other half to
In the experiment of the preceding exercise, the subjects were randomly assigned to the different treatments. What is the most important reason for this random assignment?a. Random assignment
Can a vegetarian or low-salt diet reduce blood pressure? Men with high blood pressure are assigned at random to one of four diets:(1) Normal diet with unrestricted salt;(2) Vegetarian with
Which of two brands (X or Y) of electric razor shaves closer? Researchers want to design and carry out an experiment to answer this question using 50 adult male volunteers. Here’s one idea: Have
A group of students wants to perform an experiment to determine whether Brand A or Brand B deodorant lasts longer. One group member suggests the following design: Recruit 40 student volunteers 20
Does talking on a hands-free cell phone distract drivers? Researchers recruit 40 student subjects for an experiment to investigate this question. They have a driving simulator equipped with a
Cardiologists at Athens Medical School in Greece wanted to test if chocolate affects blood vessel function. The researchers recruited 17 healthy young volunteers, who were each given a 3.5-ounce bar
Medical researchers want to compare the success rate of a new non invasive method for replacing heart valves using a cardiac catheter with traditional open-heart surgery. They have 40 male patients,
A total of 20 overweight females have agreed to participate in a study of the effectiveness of four weight-loss treatments: A, B, C, and D. The researcher first calculates how overweight each subject
A school counselor wants to compare the effectiveness of an online SAT preparation program with an in-person SAT preparation class. For an experiment, the counselor recruits 30 students who have
A nutrition experimenter intends to compare the weight gain of newly weaned male rats fed Diet A with that of rats fed Diet B. To do this, she will feed each diet to 10 rats. She has available 10
Nurse-practitioners are nurses with advanced qualifications who often act much like primary-care physicians. Are they as effective as doctors at treating patients with chronic conditions? An
The progress of a type of cancer differs in women and men. Researchers want to design an experiment to compare three therapies for this cancer. They recruit 500 male and 300 female patients who are
An agriculture researcher wants to compare the yield of 5 corn varieties: A, B, C, D, and E. The field in which the experiment will be carried out increases in fertility from north to south. The
A citrus farmer wants to know which of three fertilizers (A, B, and C) is most effective for increasing the number of oranges on his trees. He is willing to use 30 mature trees of various sizes from
A large study of 3000 Canadian children and their mothers found that the children of mothers who drank diet soda daily during pregnancy were twice as likely to be overweight at age 1 than children of
A large study used records from Canada’s national health care system to compare the effectiveness of two ways to treat prostate disease. The two treatments are traditional surgery and a new method
Does day care help low-income children stay in school and hold good jobs later in life? The Carolina Abecedarian Project (the name suggests the ABCs) has followed a group of 111 children for over 40
Do blood-building drugs help brain development in babies born prematurely? Researchers randomly assigned 53 babies, born more than a month premature and weighing less than 3 pounds, to one of three
A biologist would like to determine which of two brands of weed killer, X or Y, is less likely to harm the plants in a garden at the university. Before spraying near the plants, the biologist decides
A football coach hears that a new exercise program will increase upper body strength better than lifting weights. He is eager to test this new program in the off-season with the players on his high
People often use round prices as first offers in a negotiation. But would a more precise number suggest that the offer was more reasoned and informed? In an experiment, 238 adults played the role of
Workers who survive a layoff of other employees at their location may suffer from “survivor guilt.” A study of survivor guilt and its effects used as subjects 120 students who were offered an
Even if an experiment is double-blind, the blinding might be compromised if side effects of the treatments differ. For example, suppose researchers at a skin-care company are comparing their new acne
An experiment that claimed to show that meditation lowers anxiety proceeded as follows. The experimenter interviewed the subjects and rated their level of anxiety. Then the subjects were randomly
Refer to Exercise 56. Could blinding be used in this experiment? Explain your reasoning. Why is blinding an important consideration in this context?Exercise 56.As men age, their testosterone levels
Refer to Exercise 55. Could blinding be used in this experiment? Explain your reasoning. Why is blinding an important consideration in this context?Exercise 55.The extracts of avocado and soybean
Will cash bonuses speed the return to work of unemployed people? A state department of labor notes that last year 68% of people who filed claims for unemployment insurance found a new job within 15
A study of blood flow involved 27 healthy people aged 18 to 72. Each subject consumed a cocoa beverage containing 900 milligrams of flavonols daily for 5 days. Using a finger cuff, blood flow was
As men age, their testosterone levels gradually decrease. This may cause a reduction in energy, an increase in fat, and other undesirable changes. Do testosterone supplements reverse some of these
The extracts of avocado and soybean oils have been shown to slow cell inflammation in test tubes. Will taking avocado and soybean unsaponifiables (called ASU) help relieve pain for subjects with
The cost of a meal might affect how customers evaluate and appreciate food. To investigate, researchers worked with an Italian all-you-can-eat buffet to perform an experiment. A total of 139 subjects
Can snacking on fruit rather than candy reduce later food consumption? Researchers randomly assigned 12 women to eat either 65 calories of berries or 65 calories of candy. Two hours later, all 12
A maker of fabric for clothing is setting up a new line to “finish” the raw fabric. The line will use either metal rollers or natural-bristle rollers to raise the surface of the fabric; a
How can we reduce the rate of refusals in telephone surveys? Most people who answer at all listen to the interviewer’s introductory remarks and then decide whether to continue. One study made
Many children have their molars sealed to help prevent cavities. In an experiment, 120 children aged 6–8 were randomly assigned to a control group, a group in which sealant was applied and
A University of Helsinki (Finland) study wanted to determine if chocolate consumption during pregnancy had an effect on infant temperament at age 6 months. Researchers began by asking 305 healthy

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