Statistics: Homework 1-5 & 1-6

3 September 2022
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question
A school psychologist wants to test the effectiveness of a new method of teaching English. She recruits 100 second‚Äč-grade students and randomly divides them into two groups. Group 1 is taught by means of the new‚Äč method, while group 2 is taught by traditional methods. The same teacher is assigned to teach both groups. At the end of the‚Äč year, an achievement test is administered and the results of the two groups are compared. (a) What is the response variable in this‚Äč experiment? (b) Is the response variable qualitative or‚Äč quantitative? (c) Which of the following explanatory variables is‚Äč manipulated? ‚Äč(d) What are the‚Äč treatments? How many treatments are‚Äč there? (e) How are the factors that are not controlled dealt‚Äč with? ‚Äč(f) Which group serves as the control‚Äč group? (g) What type of experimental design is‚Äč this? ‚Äč(h) Identify the subjects. ‚Äč(i) Draw a diagram to illustrate the design.
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a. The scores on the achievement tests of both group 1 and group 2 b. The response variable is quantitative because it is a measurement c. Method of teaching d. The treatments are the new teaching method and the traditional teaching method. There are 2 treatments. e. Random assignments f. Group 2 serves as the control group because this group corresponds to the standard method that will be compared to the other method g. Completely randomized design h. The 100 students I. fig A random assignment - group A - New - Compare
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Define the following term: (a) Experimental unit
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A person, object, or some other well defined item upon which a treatment is applied.
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Consider the two questions shown below. ‚Äč(a) What is the most important problem facing the nation? ‚Äč(b) Would you be willing to pay for social media services if your user data was your personal property that the media company could not sell? Will the order in which the questions are asked affect the survey‚Äč results? If‚Äč so, what can the pollster do to alleviate this response‚Äč bias? Choose the correct answer below.
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D. No, there is no obvious reason that question order would affect the survey results in this scenario.
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What is a closed‚Äč question? What is an open‚Äč question? A. A closed question has many correct‚Äč answers, whereas an open question has only one correct answer. B. A closed question is a‚Äč free-response question, whereas an open question has fixed choices for answers. C. A closed question has fixed choices for‚Äč answers, whereas an open question is a‚Äč free-response question. D. A closed question always has yes or no‚Äč answers, whereas an open question is a‚Äč free-response question.
answer
C. A closed question has fixed choices for‚Äč answers, whereas an open question is a‚Äč free-response question.
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Discuss the advantages and disadvantages of each type of closed and open question: A. Closed questions are easier to‚Äč analyze, but limit the responses. Open questions allow respondents to state exactly how they‚Äč feel, but are harder to analyze due to the variety of answers and possible misinterpretation of answers. Your answer is correct. B. Closed questions are easier to‚Äč analyze, because they usually gather more accurate data. Open questions limit the‚Äč responses, but are harder to analyze since not every viewpoint will be covered. C. Closed questions allow respondents to state exactly how they‚Äč feel, but are harder to analyze due to the variety of answers and possible misinterpretation of answers. Open questions are easier to‚Äč analyze, but limit the responses. D. Closed questions are harder to‚Äč analyze, because they limit the responses. Open questions allow respondents to state exactly how they‚Äč feel, but are easier to analyze due to the variety of answers.
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A. Closed questions are easier to‚Äč analyze, but limit the responses. Open questions allow respondents to state exactly how they‚Äč feel, but are harder to analyze due to the variety of answers and possible misinterpretation of answers.
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What does it mean when a part of the population is‚Äč under-represented? Choose the correct answer below. A. A part of the population is‚Äč under-represented when it is proportionally smaller in a sample than in its population. Your answer is correct. B. A part of the population is‚Äč under-represented when it is proportionally smaller in its population than in a sample. C. A part of the population is‚Äč under-represented when individuals selected to be in the sample who do not respond to the survey have different opinions from those who do. D. A part of the population is‚Äč under-represented when their answers on a survey tend not to reflect their true feelings.
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A. A part of the population is‚Äč under-represented when it is proportionally smaller in a sample than in its population.
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Distinguish between nonsampling error and sampling error. A. Nonsampling error is the error that results from‚Äč undercoverage, nonresponse‚Äč bias, response‚Äč bias, or‚Äč data-entry errors. Sampling error is the error that results because a sample is being used to estimate information about a population. B. Nonsampling error is the error that results from randomness. Sampling error is the error that results from using a sample to estimate information about a population. C. Nonsampling error is the error that results from the process of obtaining the data. Sampling error is the error that results from‚Äč undercoverage, nonresponse‚Äč bias, response‚Äč bias, or‚Äč data-entry errors. D. Nonsampling error is the error that results because a sample is being used to estimate information about a population. Sampling error is the error that results from‚Äč undercoverage, nonresponse‚Äč bias, response‚Äč bias, or‚Äč data-entry errors.
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A. Nonsampling error is the error that results from‚Äč undercoverage, nonresponse‚Äč bias, response‚Äč bias, or‚Äč data-entry errors. Sampling error is the error that results because a sample is being used to estimate information about a population
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The owner of a shopping mall wishes to expand the number of shops available in the food court. He has a market researcher survey the first 120 customers who come into the food court during weekend afternoons to determine what types of food the shoppers would like to see added to the food court. Complete parts‚Äč (a) and‚Äč (b) below. ‚Äč(a) The survey has bias. Determine whether the flaw is due to the sampling method or the survey itself. For biased‚Äč surveys, identify the cause of the error. What is the cause of the‚Äč bias? A. Nonresponse B. Sampling bias C. Response bias Which of the following is the best way to remedy this‚Äč problem? A. Reword the question so that it is balanced. B. Ask customers throughout the day on both weekdays and weekends. C. Increase the sample size so that more people respond to the question
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A.Sampling bias B. Ask customers throughout the day on both weekdays and weekends
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An abortion rights advocate wants to estimate the percentage of people who favor opening abortion clinics. She conducts a nationwide survey of 1220 randomly selected adults 18 years and older. The interviewer asks the‚Äč respondents, ‚Äč"Do you favor supporting women's rights by keeping abortion clinics open?‚Äč" ‚Äč(a) Which of these best describes the bias in the‚Äč survey Which of these best describes the bias in the‚Äč survey? A. Nonresponse bias B. Response bias C. Sampling bias D. Undercoverage bias ‚Äč(b) How can the bias be‚Äč remedied? A The interviewer should survey people by phone and in person. B. The interviewer should survey a greater number of adults 18 and older. C. The interviewer should survey people under 18 as well. D. The interviewer should reword the question.
answer
(a) Response bias (b) The interviewer should reword the question
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A polling organization conducts a study to estimate the percentage of households that have more than one computer. It mails a questionnaire to 1313 randomly selected households across the country and asks the head of each household if he or she has more than one computer. Of the 1313 households‚Äč selected, 28 responded. ‚Äč(a) Which of these best describes the bias in the‚Äč survey? a. Undercoverage bias b. Response bias c. Sampling bias d. Nonresponse bias (b) How can the bias be‚Äč remedied? A. The polling organization should try contacting households that do not respond by phone or‚Äč face-to-face. B. The polling organization should mail the questionnaire to a greater number of households. C. The polling organization should mail the questionnaire to each person in the households. D. The polling organization should only select households in a single state.
answer
(a) d. Nonresponse bias (b) A. The polling organization should try contacting households that do not respond by phone or‚Äč face-to-face.
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Suppose a random phone survey is being conducted to find the population's feelings on a new Suppose a random phone survey is being conductedto find the population's feelings on a new nothing piece of technology. If the randomly selected person is not home comma they are called again piece of technology. If the randomly selected person is not home, they are called again later in the day. What tactic is being used to increase the response rate for this‚Äč survey? A. The company is selecting people randomly. B. The company is using callbacks. C. The company is using a phone survey. D. The company is using an incentive.
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B. The company is using callbacks.
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Suppose that a magazine predicted that Candidate A would defeat Candidate B in a certain election. They conducted a poll of its subscribers with a response rate of 23‚Äč%. On the basis of the‚Äč results, the magazine predicted that Candidate A would win with‚Äč 57% of the popular vote.‚Äč However, Candidate B won the election with about‚Äč 62% of the popular vote. At the time of this‚Äč poll, most subscribers to the magazine belonged to the party of Candidate A. Name two biases that led to this incorrect prediction. A. Sampling‚Äč bias: Using an incorrect frame led to undercoverage. Nonresponse‚Äč bias: The low response rate caused bias. B. Nonresponse‚Äč bias: The low response rate caused bias. Response‚Äč bias: The way the poll was administered showed bias. C. Sampling‚Äč bias: Using an incorrect frame led to undercoverage. Response‚Äč bias: The way the poll was administered showed bias.
answer
Sampling‚Äč bias: Using an incorrect frame led to undercoverage. Nonresponse‚Äč bias: The low response rate caused bias.
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What are the advantages of having a presurvey with open questions to assist in constructing a questionnaire that has closed‚Äč questions?
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The researcher can learn common answers.
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Discuss a possible advantage of offering rewards or incentives to increase response rates. Are there any‚Äč disadvantages? Discuss a possible advantage. Determine if there are any disadvantages.
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A possible advantage of offering rewards or incentives to increase response rates is that respondents put more effort into completely and accurately answering the survey questions because they feel obligated A possible disadvantage of offering rewards or incentives to increase response rates is that the people interested in the rewards or incentives differ from the population in some way that is important to the‚Äč study, causing biased results.
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Define the following term: treatment
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Any combination of the values of the factors (explanatory variables)
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Define the following term: response variable
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A quantative or qualitative variable that represents the variable of interest.
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Define the following term: factor
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The variable whose effect on the response variable is to be assessed by the experimenter
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Define the following term: placebo
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An innocuous medication, such as a sugar tablet, that looks, tastes and smells, like the experimental medication.
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Define the following term: confounding
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The effect of two factors (explanatory variables) on the response variable cannot be distinguished.
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What is replication in an‚Äč experiment? Choose the correct answer below. A. Replication is pairing up related experimental units. B. Replication is applying each treatment to more than one experimental unit. C. Replication is randomly assigning each experimental unit to a treatment. D. Replication is grouping together similar experimental units and then using random assignment
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B. Replication is applying each treatment to more than one experimental unit.
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Explain the difference between a‚Äč single-blind and a‚Äč double-blind experiment.
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In a‚Äč single-blind experiment, the subject does not know which treatment is received. In a‚Äč double-blind experiment, neither the subject nor the researcher in contact with the subject knows which treatment is received.
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Determine whether the following statement is true or false. ‚ÄčGenerally, the goal of an experiment is to determine the effect that the treatment will have on the response variable.
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True
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To help assess student learning in her music history ‚Äčcourses, a music professor at a community college implemented‚Äč pre- and‚Äč post-tests for her music history students. A‚Äč knowledge-gained score was obtained by taking the difference of the two test scores. What type of experimental design is‚Äč this? What is the response variable in this‚Äč experiment? What is the‚Äč treatment?
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Match-pairs design Difference in test scores Music History course
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Researchers wanted to evaluate whether a certain herb improved memory in elderly adults as measured by objective tests. To do‚Äč this, they recruited 92 men and 133 women older than 50 years and in good health. Participants were randomly assigned to receive the‚Äč herb, 40 mg 3 times a‚Äč day, or a matching placebo. A measure of memory improvement was determined by a standardized test of learning and memory. After 6 weeks of‚Äč treatment, the data indicated that the herb did not increase performance on standard tests of‚Äč learning, memory,‚Äč attention, and concentration. These data suggest‚Äč that, when taken following the‚Äč manufacturer's instructions, the herb provides no measurable increase in memory or related cognitive function to adults older than 50 50 years with healthy cognitive function. Complete parts‚Äč (a) through‚Äč (g) below
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a. Completely randomized design b. Adults older than 50 years and in good health c.The score on the standardized test of learning and memory d. the herb e. 40 mg 3 times a day or a matching placebo f. The 92 men and 133 women older than 50 who are in good health that participated in the study g. The placebo group
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A physician wanted to compare two types of headache relief. One type is medication and the other is using pressure points. It is a common belief that medication relieves pain faster. This belief is tested by having 10 migraine sufferers compare both types of pain relief and record their observations on a standardized scale of response. A coin flip was used to determine which type of headache relief each individual would try first. Results indicated that there was no difference in the two types of pain relief. Complete parts‚Äč (a) through‚Äč (f) below (a) What type of experimental design is‚Äč this? (b) What is the response variable? (c) What is the factor that is set to predetermined‚Äč levels? What is the‚Äč treatment? Identify the experimental units. Choose the correct answer below Why is a coin used to decide the headache relief each individual would try first headache relief each individual would try first‚Äč? Select picture:
answer
a. completely random b. The recorded observation c. The factor is the type of pain relief pain relief. The treatments are medication medication and using pressure points using pressure points. d. the migraine sufferers e. Eliminate bias as to which pain relief pain relief was used first f. assign groups & treatment
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Researchers wish to know if there is a link between hypertension‚Äč (high blood‚Äč pressure) and consumption of salt. Past studies have indicated that the consumption of fruits offsets the negative impact of salt consumption. It is also known that there is quite a bit of‚Äč person-to-person variability as far as the ability of the body to process and eliminate salt. ‚ÄčHowever, no method exists for identifying individuals who have a higher ability to process salt. It is recommended that daily intake of salt should not exceed 2300 milligrams‚Äč (mg). The researchers want to keep the design‚Äč simple, so they choose to conduct their study using a completely randomized design. Complete parts‚Äč (a) through‚Äč (c a. What is the response variable in the‚Äč study? b. Name three factors that have been identified. Select all that apply. c. For each factor‚Äč identified, determine whether the variable can be controlled or cannot be controlled. If a factor cannot be‚Äč controlled, what should be done to reduce variability in the response‚Äč variable?
answer
a. blood pressure b. body's ability to process salt, daily intake of salt, consumption of fruit c. Blood pressure is not a factor. Daily consumption of salt can be controlled. Daily consumption of fruits can be controlled. Body's ability to process salt cannot be controlled. Age is not a factor. Gender is not a factor. Experimental units should be randomized to each treatment group.