chapter summaries

Suppose you are the president of the student government. You wish to conduct a survey to determine the student​ body's opinion regarding student services. The administration provides you with a list of the names and phone numbers of the 467467 registered students. ​(a) Discuss a procedure you could follow to obtain a simple random sample of 55 students. ​(b) Obtain this sample.

(a) which of the following procedures could you follow to obtain a simple random sample of 55 ​students? Select all that apply. -List each name on a separate piece of​ paper; place them all in a​ hat, and pick five. -Number the names from 1 to 467 and use a random number table to produce 55 different​ three-digit numbers corresponding to the names selected. (b)Obtain this sample using the portion of the random number table provided in the problem statement. Start with the first column of the first row and work down each column. Type the numbers corresponding to the students chosen 354,420,69,236,208

What is a closed​ question? What is an open​ question? Discuss the advantages and disadvantages of each type of question. *What is a closed​ question? What is an open​ question? **Discuss the advantages and disadvantages of each type of question.

*A closed question has fixed choices for​ answers, whereas an open question is a​ free-response question. **closed questions are easier to​ analyze, but limit the responses. Open questions allow respondents to state exactly how they​ feel, but are harder to analyze due to the variety of answers and possible misinterpretation of answers.

A polling organization contacts 1591 adult men who are 40 to 60 years of age and live in the United States and asks whether or not they had seen their family nbsp doctor within the past 6 months. *What is the population in the​ study? **What is the sample in the​ study?

*Adult men who are 40 to 60 years of age and live in the United states. **The 1591 adult men who are 40 to 60 years of age andand live in the United states

A polling organization contacts 29022902 female university graduatesfemale university graduates whowho have a white collar jobhave a white collar job and asks whether or not they had received a raise atreceived a raise atnbsp work nbsp work during the past 6 monthsduring the past 6 months. *What is the population in the​ study? **What is the sample in the​ study?

*Female university graduatesFemale university graduates whowho have a white collarhave a white collar job. **The 2902 female university graduates female university graduates who have a white collar job

A school psychologist wants to test the effectiveness of a new method of teaching Logic.Logic. She recruits 200200 fourthfourth​-grade students and randomly divides them into two groups. Group 1 is taught by means of the new​ method, while Group 2 is taught via traditional methods. The same teacher is assigned to teach both groups. At the end of the​ year, an achievement test is administered and the results of the two groups compared. *What is the response variable in this​ experiment? **Which of the following explanatory variables is​ manipulated? ***How many levels of the treatment are​ there? ****What type of experimental design is​ this? *****Identify the subjects.

*The score on the achievement test **Method of teaching *** 2 ****Completely randomized assignment *****The 200 students

What are some solutions to​ nonresponse?

-attempt callbacks -offer rewards and incentives

A salesperson obtained a systematic sample of size 30 from a list of 750 clients. To do​ so, he randomly selected a number from 1 to 25​, obtaining the number 17. He included in the sample the 17th client on the list and every 25th client there after. List the numbers that correspond to the 30 clients selected.

17​, 42​, ​..., 742

What is a designed​ experiment?

A designed experiment is when a researcher assigns individuals to a certain​ group, intentionally changing the value of an explanatory​ variable, and then recording the value of the response variable for each group.

A small community college employs 5252 ​full-time faculty members. To gain the​ faculty's opinions about upcoming contract​ negotiations, the president of the faculty union wishes to obtain a simple random sample that will consist of 5 faculty members. She numbers the faculty 1 to 5252. 26,21,47,37,26,27,1,33,35 First chosen​ member: second chosen​ member: third chosen​ member: fourth chosen​ member: fifth chosen​ member:

26 21 47 37 27

Which allows the researcher to claim causation between an explanatory variable and a response​ variable?

A designed experiment

What is a lurking​ variable? Choose the correct answer below

A lurking variable is an explanatory variable that was not considered in a​ study, but that affects the value of the response variable in the study. In​ addition, lurking variables are typically related to explanatory variables in the study.

In an attempt to identify ecologically friendly methods for controlling mosquito​ populations, researchers conducted field experiments in a certain country where aquatic nymphs of the dragonfly Brachytron pretense were used against the larvae of mosquitoes. The researchers concluded that Brachytron pretense can be used effectively as a​ strong, ecologically friendly control of mosquitoes and​ mosquito-borne diseases. Complete parts​ (a) through​ (i).

A. Since the researchers want to answer the question if nymphs of Brachytron pretense will control​ mosquitoes, the research objective is to determine if nymphs of Brachytron pretense will control mosquitoes. B. A completely randomized design because the experimental units are randomly assigned to a treatment c. Mosquito larvae density because the researcher measured mosquito larvae density The response variable is "quantitative because mosquito larvae density is a numerical measure" d. Introduction of nymphs of Brachytron pretense into water tanks containing mosquito larvae because this affected larvae of mosquitoes Nymphs added or no nymphs added because this is a possible combination of the values of the factor e.Yes because​ temperature, for​ example, may affect larvae of mosquitoes f. All mosquito larvae in all breeding places because this is an entire group of individuals that was studied The mosquito larvae in the ten 400400​-liter ​outdoor, open concrete water tanks because this is a subset of the population that was studied g. During the study​ period, mosquito larvae density changed from 7.34 to 0.850.85 to 6.83 larvae per dip in the treatment​ tanks, while changing from 7.12 to 6.83 to 6.776.77 larvae per dip in the control tanks. h. The researchers controlled the experiment by first clearing the ten tanks of all nonmosquito​ larvae, nymphs, and fish so that only mosquito larvae were left in the tanks. In this way the researchers attempted to make the tanks as identical as​ possible, except for the treatment. i. Since over the period of 1010 ​days, the​ nymph-treated tanks did show a significant difference in larval​ density, nymphs of Brachytron pretense can be used effectively as a​ strong, ecologically friendly control of mosquitoes and​ mosquito-borne diseases because the​ nymph-treated tanks did show a significant difference in larval​ density, while the control tanks did not show a significant difference in larval density.

A poll is being conducted outside of a schooloutside of a school nothingto obtain a sample of the population of an entire country. What is the frame for this type of​ sampling? Who would be excluded from the survey and how might this affect the results of the​ survey? A. what is the free for this type of sampling? b. who would be excluded from the survey and how might this affect the results on the survey?

A. The frame is the entire population of the country. B. Any person who does not go to that schoolAny person who does not go to that school is excluded.is excluded. This could result in sampling bias due to undercoverage.

A school psychologist wants to test the effectiveness of a new method of teaching Statistics. She recruits 100 fifth​-grade students and randomly divides them into two groups. Group 1 is taught by means of the new​ method, while Group 2 is taught via traditional methods. The same teacher is assigned to teach both groups. At the end of the​ year, an achievement test is administered and the results of the two groups compared. a. What is the response variable in this​ experiment? b.Which of the following explanatory variables is​ manipulated? c. How many levels of the treatment are​ there? d. What type of experimental design is​ this? e.Identify the subjects.

A. The score on the achievement test b.Method of teaching c. 2 d. What type of experimental design is​ this? e. the 400 students

Researchers wanted to determine if there was an association between daily coffee consumption and the occurrence of skin cancer. The researchers looked at 94 comma 60694,606 women and asked them to report their​ coffee-drinking habits. The researchers also determined which of the women had nonmelanoma skin cancer. After their​ analysis, the researchers concluded that consumption of six or more cups of caffeinated coffee per day was associated with a reduction in nonmelanoma skin cancer. Complete parts​ (a) through​ (c).

A. This was a​ cross-sectional study because all information about the individuals was collected at a specific point in time. B. The response variable is whether the woman has nonmelanoma skin cancer or not. c. The explanatory variable is consumption of caffeinated coffee. d. The researchers may be concerned with confounding that occurs when the effects of two or more explanatory variables are not separated or when there are some explanatory variables that were not considered in a​ study, but that affect the value of the response variable.

A student wanted to compare two types of commuting options. One type is carpooling and the other is taking a commuter train. It is a common belief that carpooling saves more time. This belief is tested by having 10 students commute to school by each mode of transportation and record the time of arrival at school each morning. A coin flip was used to determine which type of transportation that a student would use first. Results indicated that there was no difference in the two types of transportation. a. what type of experimental design is this? b. what is the response variable in this experiment? c. what is the treatment? d. what are the experimental units? e. why is coin used to decide the transportation that a student would use first?

A. matched pair b. the time of arrival c. the types of transportation d.the students e. to eliminate bias as to which transportation was used first

An antigun advocate wants to estimate the percentage of people who favor stricter gun laws. He conducts a nationwide survey of 1,203 randomly selected adults 18 years old and older. The interviewer asks the respondents, "Do you favor harsher penalties for individuals who sell guns illegally? " This survey has bias. ​(a) What is the type of​ bias? ​(b) What is a possible​ remedy?

A.Response bias B.reword the question

Researchers wanted to determine if having a television​ (TV) in the bedroom is associated with obesity. The researchers administered a questionnaire to 3368 ​twelve-year-old adolescents. After analyzing the​ results, the researchers determined that the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom. Complete parts​ (a) through​ (e).

A.This is an observational study because the researchers observe the behavior of the individuals in the study without trying to influence an explanatory variable of the study. cross-sectonal study b. The response variable is the body mass index of the adolescents. c.The explanatory variable is whether the adolescent has a TV in the bedroom or not. d. the researchers made an effort to avoid confounding by accounting for potential lurking variables. e ​No, a television in the bedroom and obesity are associated because the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom.

What is an observational​ study?

An observational study measures the value of the response variable without attempting to influence the value of either the response or explanatory variables.

What is a​ case-control study? Choose the correct answer below.

Case-control studies are observational studies that are​ retrospective, meaning that they require individuals to look back in time or require the researcher to look at existing records.

What is meant by​ confounding? Choose the correct answer below.

Confounding in a study occurs when the effects of two or more explanatory variables are not separated.​ Therefore, any relation that may exist between an explanatory variable and the response variable may be due to some other variable or variables not accounted for in the study.

What is a​ cross-sectional study? Choose the correct answer below.

Cross-sectional studies are observational studies that collect information about individuals at a specific point in time or over a very short period of time.

Determine whether the following statement is true or false. Explain. A simple random sample is always preferred because it obtains the same information as other sampling plans but requires a smaller sample size.

False, because other sampling techniques may provide more information for less cost than a simple random sample.

Determine whether the following statement is true or false. Explain. When obtaining a stratified​ sample, the number of individuals included within each stratum must be equal.

False. Within stratified​ samples, the number of individuals sampled from each stratum should be proportional to the size of the strata in the population.

Determine the level of measurement of the variable. Time of day measured in military time: 1500, 1600, 1700, 1800, and 1900

Interval

Which is the superior observational​ study? Why? Choose the correct answer below.

Neither study is always the superior to the other. Both have advantages and disadvantages that depend on the situation.

Determine whether the study depicts an observational study or an experiment. While shopping 325 people are asked to perform a taste test in which they drink two randomly placed, unmarked coffees and asked which they prefer.

The study is an observational study because the study examines individuals in a​ sample, but does not try to influence the variable of interest

Is the value a parameter or a​ statistic

The value is a statistic because the 6,076 adults in public rest rooms is a sample.

"Volume of gravel in a pile" Is the variable discrete or​ continuous?

The variable is continuouscontinuous because it is notis not countable.

Determine whether the variable is qualitative or quantitative. Favorite musical instrument

The variable is qualitative because it is an attribute characteristic.

For a poll of voters regarding a referendum calling for a national railways development program, design a sampling method to obtain the inviduals in the sample. Be sure to support your choice. Which sampling method would most likely be used in a poll of voters regarding a referendum calling for a national railways development program?

Use stratified random sampling. Since this is a national​ issue, different geographical locations are likely to have similar views.

A consumer wanted to compare two types of battery storage. One type is refrigerated and the other is room temperature. It is a common belief that refrigerated batteries last longer. This belief is tested by placing 10 fully minus charged batteries into each type of storage and placing 10 fully−charged batteries into each type of storage and then measuring the percentage of charge remaining after thirty days.then measuring the percentage of charge remaining after thirty days. A coin flip was used to determine which type of storage each battery would be placed in first storage each battery would be placed in first. Results indicated that there was no difference in the two types of storage.

What type of experimental design is​ this? -Matched pair What is the response variable in this​ experiment? -The remaining chargeremaining charge What is the​ treatment? -The types of storage What are the experimental​ units? -The batteries Why is a coin used to decide the storage each battery would be placed in firststorage each battery would be placed in first​? -To eliminate bias as to which storage was used first

A club wants to sponsor a panel discussion on the upcoming national election. The club wants fourfour of its members to lead the panel discussion. Write a short description of the processes that can be used to generate your sample. Obtain a simple random sample of size 44 from the table.

Which of the following would produce a simple random​ sample? Select all that apply. -List each name on a separate piece of​ paper, place them all in a​ hat, and pick four. -Number the names from 1 to 25 and use a random number table to produce 44 different two digit numbers corresponding to the names selected. Use the portion of the random number table provided to obtain a simple random sample of size 44 from this list. If you start with the first column of the first​ row, work down each​ column, and take the first fourfour numbers between 1 and​ 25, what fourfour members would be selected from the numbered​ list? -Keating comma Lukens comma Tate comma NolanKeating, Lukens, Tate, Nolan Ramirez comma Grajewski comma Hamilton comma TateRamirez, Grajewski, Hamilton, Tate

a. experimental unit b.treatment c.response variable d.factor e. placebo f. confounding

a. A​ person, object, or some other​ well-defined item upon which a treatment is applied b. Any combination of the values of the factors​ (explanatory variables) c. The quantitative or qualitative variable for which the experimenter wishes to determine how its value is affected by the explanatory variable d. A variable whose effect on the response variable is to be assessed by the experimenter e. An innocuous​ medication, such as a sugar​ tablet, that​ looks, tastes, and smells like the experimental medication f. The effect of two factors​ (explanatory variables on the response​ variable) cannot be distinguished.

A study conducted by researchers was designed​ "to determine if application of duct tape is as effective as cryotherapy in the treatment of common​ warts." The researchers randomly divided 60 patients into two groups. The 30 patients in group 1 had their warts treated by applying duct tape. The 30 patients in group 2 had their warts treated by cryotherapy. Once the treatments were​ complete, it was determined that 50​% of the patients in group 1 and 40​% of the patients in group 2 had complete resolution of their warts. The researchers concluded that duct tape is significantly more effective in treating warts than cryotherapy. ​(a) Identify the research objective. Which of the following is​ correct? ​(b) Identify the sample. Which of the following is​ correct? ​(c) List the descriptive statistics. Which of the following is​ correct? ​(d) State the conclusion of the study. Which of the following is​ correct?

a. To determine if duct tape is as effective as cryotherapy in treating warts. b. The 60 patients with warts. c. 60​% of patients in group 1 and 50​% of patients in group 2 with complete resolution. d. Duct tape is significantly more effective than cryotherapy in treating warts.

To estimate the percentage of defects in a recent manufacturing​ batch, a quality control manager at Toshiba selects every 19th laptop that comes off the assembly line starting with the third until she obtains a sample of 130 laptops. what type of sampling is used?

systematic

Determine whether the study depicts an observational study or an experiment. Forty people are divided into two groups. One group is exposed to atonal classical music. The other is not. After one month, both groups are questioned about their ability to remember random phrases.

the study is an experiment because the researchers control one variable to determine the effect on the response variable.

Suppose you are the president of the student government. You wish to conduct a survey to determine the student​ body's opinion regarding student services. The administration provides you with a list of the names and phone numbers of the 561 registered students. ​(a) Discuss a procedure you could follow to obtain a simple random sample of 55 students. ​(b) Obtain this sample.

​(a) Which of the following procedures could you follow to obtain a simple random sample of 55 ​students? Select all that apply. -List each name on a separate piece of​ paper; place them all in a​ hat, and pick five. -Number the names from 1 to 561 and use a random number table to produce 55 different​ three-digit numbers corresponding to the names selected. ​(b) Obtain this sample using the portion of the random number table provided in the problem statement. Start with the first column of the first row and work down each column. Type the numbers corresponding to the students chosen. -376, 352 , 192, 45 , 482