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elementary statistics

Elementary Statistics 3rd Edition William Navidi, Barry Monk - Solutions

In a _________________study, a group of subjects is studied to determine whether various factors of interest are associated with an outcome.In Exercises 5–10, fill in each blank with the appropriate word or phrase.
To determine his constituents’ feelings about election reform, a politician sends a survey to people who have subscribed to his newsletter. More than 1000 responses are received.In Exercises 9–16, specify the type of bias involved.
A sample that is not drawn by a well-defined random method is called a _______.In Exercises 7–12, fill in each blank with the appropriate word or phrase.
A poll is conducted of 3500 households close to major national airports, and another 2000 that are not close to an airport, in order to study whether living in a noisier environment results in health effects. Is this a randomized experiment or an observational study?
Qualitative variables describe how much or how many of something there is.In Exercises 11–14, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
To determine whether using a cell phone while driving increases the risk of an accident, a researcher examines accident reports to obtain data about the number of accidents in which a driver was talking on a cell phone.a. Is this a randomized experiment or an observational study?b. Assume that the
In a randomized experiment, the treatment groups do not differ in any systematic way except that they receive different treatments.In Exercises 11–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
An e-store that sells cell phone accessories reports that 98% of its customers are satisfied with the speed of delivery.In Exercises 9–16, specify the type of bias involved.
A _______ sample is one in which the population is divided into groups and a random sample of groups is drawn.In Exercises 7–12, fill in each blank with the appropriate word or phrase.
In a study, 200 patients with skin cancer are randomly divided into two groups. One group receives an experimental drug and the other group receives a placebo. Is this a randomized experiment or an observational study?
A nominal variable is a qualitative variable with no natural ordering.In Exercises 11–14, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
The English department at a local college is considering using electronic-based assignment submission in its English composition classes. To study its effects, each section of the class is divided into two groups at random. In one group, assignments are submitted by turning them in to the professor
A confounder makes it easier to draw conclusions from a study.In Exercises 11–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
A sign in a restaurant claims that 95% of their customers believe them to have the best food in the world.In Exercises 9–16, specify the type of bias involved.
A _______ sample is one in which the population is divided into groups and a random sample is drawn from each group.In Exercises 7–12, fill in each blank with the appropriate word or phrase.
In a randomized experiment, if there are large differences in outcomes among treatment groups, we can conclude that the differences are due to the _____________________.
A discrete variable is one whose possible values can be listed.In Exercises 11–14, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
The TV columnist for a local newspaper invites readers to log on to a website to vote for their favorite TV newscaster.In Exercises 13–15, explain why the results of the studies described are unreliable.
In an observational study, subjects are assigned to treatment groups at random.In Exercises 11–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
A television newscaster invites viewers to tweet their opinions about whether the U.S. Congress is doing a good job in handling the economy. More than 100,000 people send in an opinion.In Exercises 9–16, specify the type of bias involved.
A sample of convenience is never acceptable.In Exercises 13–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
In analyzing the course grades of students in an elementary statistics course, a professor notices that students who are seniors performed better than students who are sophomores. The professor is tempted to conclude that older students perform better than younger ones. Describe a possible
A person’s height is an example of a continuous variable.In Exercises 11–14, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
A life insurance company wants to study the life expectancy of people born in 1950. The company’s actuaries examine death certificates of people born in that year to determine how long they lived.In Exercises 13–15, explain why the results of the studies described are unreliable.
A police department conducted a survey in which police officers interviewed members of their community to ask their opinions on the effectiveness of the police department. The police chief reported that 90% of the people interviewed said that they were satisfied with the performance of the police
Observational studies are generally more reliable than randomized experiments.In Exercises 11–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
In a cluster sample, the population is divided into groups, and a random sample from each group is drawn.In Exercises 13–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
True or false: The way that questions are worded on a survey may have an effect on the responses.
Your best friend’s name.In Exercises 15–24, determine whether the data described are qualitative or quantitative.
A congressman sent out questionnaires to 10,000 constituents to ask their opinions on a new health-care proposal. A total of 200 questionnaires were returned, and 70% of those responding supported the proposal.In Exercises 13–15, explain why the results of the studies described are unreliable.
In a case-control study, the outcome has occurred before the subjects are sampled.In Exercises 11–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
In a study of the effectiveness of wearing seat belts, a group of people who had survived car accidents in which they had not worn seat belts reported that seat belts would not have helped them.In Exercises 9–16, specify the type of bias involved.
Both stratified sampling and cluster sampling divide the population into groups.In Exercises 13–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
A radio talk show host invites listeners to call the show to express their opinions about a political issue. How reliable is this survey? Explain.
Your best friend’s age.In Exercises 15–24, determine whether the data described are qualitative or quantitative.
In a cross-sectional study, measurements are made at only one point in time.In Exercises 11–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement.
The title of your statistics book In Exercises 15–24, determine whether the data described are qualitative or quantitative.
A medical researcher wants to determine whether exercising can lower blood pressure. At a health fair, he measures the blood pressure of 100 individuals, and interviews them about their exercise habits. He divides the individuals into two categories: those whose typical level of exercise is low,
Random-digit dialing is a sampling method in which a computer generates phone numbers at random to call. In recent years, caller ID has become popular.Do you think that caller ID increases the bias in random digit dialing? Explain.
The average age of the employees in a certain company is 35 years.In Exercises 17–20, determine whether the number described is a statistic or a parameter.
The number of files on a computer In Exercises 15–24, determine whether the data described are qualitative or quantitative.
A medical researcher wants to determine whether exercising can lower blood pressure. She recruits 100 people with high blood pressure to participate in the study. She assigns a random sample of 50 of them to pursue an exercise program that includes daily swimming and jogging. She assigns the other
Many polls are conducted over the telephone. Some polling organizations choose a sample of phone numbers to call from lists that include landline phone numbers only, and do not include cell phones.Do you think this increases the bias in phone polls?Explain.
Of the students enrolled in a certain college, 80% are full-time.In Exercises 17–20, determine whether the number described is a statistic or a parameter.
The waist size of a pair of jeansIn Exercises 15–24, determine whether the data described are qualitative or quantitative.
An agricultural scientist wants to determine the effect of fertilizer type on the yield of tomatoes. There are four types of fertilizer under consideration. She plants tomatoes on four plots of land. Each plot is treated identically except for receiving a different type of fertilizer.a. What are
When multiple-choice questions are asked, the order of the choices is usually changed each time the question is asked. For example, in the 2016 presidential election, a pollster would ask one person ‘‘Who do you prefer for president, Hillary Clinton or Donald Trump?” For the next person, the
In a survey of 500 high school students, 60% of them said that they intended to go to college.In Exercises 17–20, determine whether the number described is a statistic or a parameter.
The ingredients in a recipe In Exercises 15–24, determine whether the data described are qualitative or quantitative.
A scientist wants to determine whether people who live in places with high levels of air pollution get more colds than people in areas with little air pollution. Do you think it is possible to design a randomized experiment to study this question, or will an observational study be necessary?
In the 1936 presidential election, Republican candidate Alf Landon challenged President Franklin Roosevelt. The Literary Digest magazine conducted a poll in which they mailed questionnaires to more than 10 million voters. The people who received the questionnaires were drawn from lists of
Draw a simple random sample of eight animals from the list of 40 animals in the table.Exercises 21–24 refer to the population of animals in the following table. The population is divided into four groups:mammals, birds, reptiles, and fish. Mammals Birds 1. Aardvark 6. Lion 11. Flamingo 16. Hawk
Your school colors In Exercises 15–24, determine whether the data described are qualitative or quantitative.
A scientist wants to determine whether a new cold medicine relieves symptoms more effectively than a currently used medicine. Do you think it is possible to design a randomized experiment to study this question, or will an observational study be necessary?Explain.
Draw a sample of eight animals by drawing a simple random sample of two animals from each group. What kind of sample is this?Exercises 21–24 refer to the population of animals in the following table. The population is divided into four groups:mammals, birds, reptiles, and fish. Mammals Birds 1.
The makes of cars sold by a particular car dealer In Exercises 15–24, determine whether the data described are qualitative or quantitative.
A sociologist discovered that regions that have more taxicabs tend to have higher crime rates. Does increasing the number of taxicabs cause the crime rate to increase, or could the result be due to confounding?Explain.
Draw a simple random sample of two groups of animals from the four groups, and construct a sample of 20 animals by including all the animals in the sampled groups.What kind of sample is this?Exercises 21–24 refer to the population of animals in the following table. The population is divided into
The number of cars sold by a car dealer last month In Exercises 15–24, determine whether the data described are qualitative or quantitative.
Choose a random number between 1 and 5.Include the animal with that number in your sample, along with every fifth animal thereafter, to construct a sample of eight animals. What kind of sample is this?Exercises 21–24 refer to the population of animals in the following table. The population is
In a study of people who had suffered heart attacks, it was found that those who lived in smaller houses were more likely to recover than those who lived in larger houses. Does living in a smaller house increase the likelihood of recovery from a heart attack, or could the result be due to
The categories Strongly disagree, Disagree, Neutral, Agree, and Strongly agree on a survey In Exercises 25–32, determine whether the data described are nominal or ordinal.
In an observational study, people who ate four or more servings of fresh fruits and vegetables each day were less likely to develop colon cancer than people who ate little fruit or vegetables. True or false:a. The results of the study show that eating more fruits and vegetables reduces your risk of
A college faculty consists of 400 men and 250 women. The college administration wants to draw a sample of 65 faculty members to ask their opinion about a new parking fee. They draw a simple random sample of 40 men and another simple random sample of 25 women.In Exercises 25–36, identify the kind
The names of the counties in a state In Exercises 25–32, determine whether the data described are nominal or ordinal.
A vocabulary test was given to students at an elementary school. The students’ ages ranged from 5 to 11 years old. It was found that the students with larger vocabularies tended to be taller than the students with smaller vocabularies. Explain how this result might be due to confounding.
A pollster walks around a busy shopping mall, and approaches people passing by to ask them how often they shop at the mall.In Exercises 25–36, identify the kind of sample that is described.
The shirt sizes of Small, Medium, Large, and X-Large In Exercises 25–32, determine whether the data described are nominal or ordinal.
A recent study compared the heart rates of 19 infants born to nonsmoking mothers with those of 17 infants born to mothers who smoked an average of 15 cigarettes a day while pregnant and after giving birth.The heart rates of the infants at one year of age were 20% slower on the average for the
A pollster obtains a list of all the residential addresses in a certain town, and uses a computer random number generator to choose 150 of them. The pollster visits each of the 150 households and interviews all the adults in each household about their television viewing habits.In Exercises 25–36,
I got an A in statistics, a B in biology, and C’s in history and English.In Exercises 25–32, determine whether the data described are nominal or ordinal.
In a recent study, Z. Zhao and colleagues measured the levels of formaldehyde in the air in 34 classrooms in the schools in the city of Taiyuan, China. On the same day, they gave questionnaires to 1993 students aged 11–15 in those schools, asking them whether they had experienced respiratory
Police at a sobriety checkpoint pull over every fifth car to determine whether the driver is sober.In Exercises 25–36, identify the kind of sample that is described.
This semester, I am taking statistics, biology, history, and English.In Exercises 25–32, determine whether the data described are nominal or ordinal.
In 1954, the first vaccine against polio, known as the Salk vaccine, was tested in a large randomized double-blind study. Approximately 750,000 children were asked to enroll in the study. Of these, approximately 350,000 did not participate, because their parents refused permission. The children who
A television newscaster invites viewers to tweet their opinions on a proposed bill on immigration policy. More than 50,000 people express their opinions in this way.In Exercises 25–36, identify the kind of sample that is described.
I ordered a pizza with pepperoni, mushrooms, olives, and onions.In Exercises 25–32, determine whether the data described are nominal or ordinal.
Another study of the Salk vaccine, conducted at the same time as the trial described in Exercise 29, used a different design. In this study, approximately 350,000 second graders were invited to participate. About 225,000 did so, and the other 125,000 refused. All of the participating second graders
The superintendent of a large school district wants to test the effectiveness of a new program designed to improve reading skills among elementary school children.There are 30 elementary schools in the district.The superintendent chooses a simple random sample of five schools, and institutes the
In the track meet, I competed in the high jump and the pole vault.In Exercises 25–32, determine whether the data described are nominal or ordinal.
A study was performed by the Public Health Service on the health of smokers and former smokers.The results showed that current smokers were healthier than people of the same age who had recently quit smoking. Is it reasonable to conclude that smokers become less healthy after they quit? If not,
All the customers who entered a store on a particular day were given a survey to fill out concerning their opinions of the service at the store.In Exercises 25–36, identify the kind of sample that is described.
I finished first in the high jump and third in the pole vault.In Exercises 25–32, determine whether the data described are nominal or ordinal.
It is known that alcohol consumption increases the risk of liver disease. A study finds that the rate of liver disease is higher among smokers than nonsmokers. Is it reasonable to conclude that smoking increases the risk of liver disease? What other explanation can you give?
Five hundred people attend a charity event, and each buys a raffle ticket. The 500 ticket stubs are put in a drum and thoroughly mixed, and 10 of them are drawn. The 10 people whose tickets are drawn win a prize.In Exercises 25–36, identify the kind of sample that is described.
The amount of caffeine in a cup of Starbucks coffee In Exercises 33–40, determine whether the data described are discrete or continuous.
The director of a hospital pharmacy chooses at random 100 people age 60 or older from each of three surrounding counties to ask their opinions of a new prescription drug program.In Exercises 25–36, identify the kind of sample that is described.
The distance from a student’s home to his school In Exercises 33–40, determine whether the data described are discrete or continuous.
Officials at a metropolitan transit authority want to get input from people who use a certain bus route about a possible change in the schedule. They randomly select 5 buses during a certain week and poll all riders on those buses about the change.In Exercises 25–36, identify the kind of sample
The number of steps in a stairwayIn Exercises 33–40, determine whether the data described are discrete or continuous.
A retailer samples 25 receipts from the past week by numbering all the receipts, generating 25 random numbers, and sampling the receipts that correspond to these numbers.In Exercises 25–36, identify the kind of sample that is described.
The number of students enrolled at a college In Exercises 33–40, determine whether the data described are discrete or continuous.
A cell phone company wants to draw a sample of 600 customers to gather opinions about potential new features on upcoming phone models. The company draws a random sample of 200 from customers with iPhones, a random sample of 100 from customers with LG phones, a random sample of 100 from customers
The amount of charge left in the battery of a cell phone In Exercises 33–40, determine whether the data described are discrete or continuous.
Every third day, a computer network administrator analyzes the company’s network logs to check for signs of computer viruses.
The number of patients who reported that a new drug had relieved their pain In Exercises 33–40, determine whether the data described are discrete or continuous.
smartphone app produces a message requesting customers to click on a link to rate the app.
The number of electrical outlets in a coffee shop In Exercises 33–40, determine whether the data described are discrete or continuous.
A pharmaceutical company wants to test a new drug that is designed to provide superior relief from headaches. They want to select a sample of headache sufferers to try the drug.Do you think that it is feasible to draw a simple random sample of headache sufferers, or will it be necessary to use a
The time it takes for a text message to be delivered In Exercises 33–40, determine whether the data described are discrete or continuous.

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