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Ch. 1 - Introduction to Statistics
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446당신이 사용하는 게 아니라요?교과서 변경
1장, 문제 1.2.30

In Exercises 29–32, identify the level of measurement of the data as nominal, ordinal, interval, or ratio. Also, explain what is wrong with the given calculation.
Social Security Numbers As part of a project in a statistics class, students report the last four digits of their Social Security numbers, and the average (mean) of those digits is computed to be 4.7.

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1
Identify the level of measurement: Social Security numbers are identifiers and do not have a meaningful order or zero point. Therefore, they are measured at the nominal level.
Explain the nominal level: The nominal level of measurement is used for data that are categories without any intrinsic ordering. Examples include names, labels, or categories.
Discuss the inappropriateness of the calculation: Since Social Security numbers are nominal data, it is inappropriate to perform arithmetic operations such as calculating the mean.
Clarify why the mean is inappropriate: The mean is a measure of central tendency that requires interval or ratio level data, where the numbers have meaningful differences and a true zero point.
Conclude with the correct approach: For nominal data like Social Security numbers, appropriate analyses might include counting frequencies or identifying modes, but not calculating means.

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주요 개념

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Levels of Measurement

Levels of measurement refer to the different ways data can be categorized, which include nominal, ordinal, interval, and ratio. Nominal data are labels without any quantitative value, ordinal data have a meaningful order but no consistent difference between values, interval data have consistent differences but no true zero, and ratio data have both consistent differences and a true zero, allowing for meaningful ratios.
추천 영상:
10:28
Difference in Proportions: Hypothesis Tests Example 1

Nominal Data

Nominal data are used for labeling variables without any quantitative value. In the context of Social Security numbers, these numbers serve as identifiers and do not have any inherent numerical value or order. Therefore, they are considered nominal data, which means calculating a mean or average is not meaningful or appropriate.
추천 영상:
04:39
Visualizing Qualitative vs. Quantitative Data

Inappropriate Calculations with Nominal Data

Calculating the mean of nominal data is inappropriate because nominal data are categorical and do not possess numerical properties that allow for arithmetic operations. Social Security numbers are identifiers, and averaging them does not yield a meaningful result, as they do not represent quantities or measurements that can be averaged.
추천 영상:
04:39
Visualizing Qualitative vs. Quantitative Data
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In Exercises 9–12, determine whether the sampling method appears to be sound or is flawed.


Clinical Trials Researchers at Yale University conduct a wide variety of clinical trials by using subjects who volunteer after reading advertisements soliciting paid volunteers.

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Parameter and Statistic In a Citrix Security survey of 1001 adults in the United States, it was found that 69% of those surveyed believe that having their personal information stolen is inevitable. Identify the population and sample. Is the value of 69% a statistic or a parameter?

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교과서 질문

In Exercises 9–20, identify which of these types of sampling is used: random, systematic, convenience, stratified, or cluster.

Reported and Observed Results A Harris Interactive study involved 1013 adults who were interviewed about washing their hands in restrooms and another 6336 adults who were observed in public restrooms.

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In Exercises 37–44, answer the given questions, which are related to percentages.

Checking Job Applicants In a study conducted by the Society for Human Resource Management, 347 human resource professionals were surveyed. Of those surveyed, 73% said that their companies conduct criminal background checks on all job applicants.


a. What is the exact value that is 73% of the 347 survey subjects?

b. Could the result from part (a) be the actual number of survey subjects who said that their companies conduct criminal background checks on all job applicants? Why or why not?

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Computer Virus In an AOL survey of Internet users, this question was posted online: “Have you ever been hit by a computer virus?” Among the 170,063 responses, 63% answered “yes.” What term is used to describe this type of survey in which the people surveyed consist of those who chose to respond? What is wrong with this type of sampling method?

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Sampling Method The patients were recruited among those at a Veterans Affairs hospital. What type of sampling best describes the way in which the subjects were chosen: simple random sample, systematic sample, convenience sample, stratified sample, cluster sample? Does the method of sampling appear to adversely affect the quality of the results?

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