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Chapter 1: Problem 21

With the increasing popularity of online shopping, many consumers use Internet access at work to browse and shop online. In fact, the Monday after Thanksgiving has been nicknamed "Cyber Monday" because of the large increase in online purchases that occurs that day. Data from a large-scale survey by a market research firm (Detroit Free Press, November 26,2005\()\) were used to calculate estimates of the percentage of men and women who shop online while at work. The resulting estimates probably won't make most employers happy \(-42 \%\) of the men and \(32 \%\) of the women surveyed were shopping online at work! If the population of interest is working men and women, does the group of people surveyed represent a census or a sample? Are the percentages quoted (42\% for men and \(32 \%\) for women) statistics or population characteristics?

Short Answer

Expert verified
The group of people surveyed represents a 'sample' and not a 'census', and the percentages quoted (42% for men and 32% for women) are 'statistics' and not population characteristics.

Step by step solution

01

Understanding the terms

A 'sample' refers to a subset of a larger group, or population, that is selected for observation. In contrast, a 'census' refers to an analysis that includes every member of the population. 'Statistics' are numeric values that describe attributes of a sample, while 'population characteristics' are actual percentages or ratios that represent attributes of an entire population.
02

Determining if it’s a sample or a census

The research firm surveyed a large group of working men and women, and they certainly did not survey every single working man and woman. Therefore, the group of people surveyed represents a 'sample' and not a 'census'.
03

Determining if they are statistics or population characteristics

The percentages quoted (42% for men and 32% for women) are based on the sample surveyed, not the entire population. They are 'statistics' because they are derived from the sample to describe specific attributes of it, and not confirmed attributes of the entire population.

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Most popular questions from this chapter

For each of the following, determine whether the statistical study described is an observational study or an experiment. Give a brief explanation of your choice. a. Can choosing the right music make wine taste better? This question was investigated by a researcher at a university in Edinburgh (www.decanter.com/news). Each of 250 volunteers was assigned at random to one of five rooms where they were asked to taste and rate a glass of wine. No music was playing in one of the rooms, and a different style of music was playing in each of the other four rooms. The researcher concluded that cabernet sauvignon is rated more highly when bold music is played than when no music is played. b. The article "Display of Health Risk Behaviors on MySpace by Adolescents" (Archives of Pediatrics and Adolescent Medicine [2009]: 27-34) described a study of 500 publically accessible MySpace web profiles posted by 18-year- olds. The content of each profile was analyzed and the researchers concluded that those who indicated involvement in sports or a hobby were less likely to have references to risky behavior (such as sexual references or references to substance abuse or violence) c. USA Today (January 29,2003 ) reported that in a study of affluent Americans (defined as those with incomes of \(\$ 75,000\) or more per year) \(57 \%\) indicated that they would rather have more time than more money. d. The article "Acupuncture for Bad Backs: Even Sham Therapy Works" (Time, May 12,2009 ) summarized a study conducted by researchers at the Group Health Center for Health Studies in Seattle. In this study, 638 adults with back pain were randomly assigned to one of four groups. People in group 1 received the usual care for back pain. People in group 2 received acupuncture at a set of points tailored specifically for each individual. People in group 3 received acupuncture at a standard set of points typically used in the treatment of back pain. Those in group 4 received fake acupuncture-they were poked with a toothpick at the same set of points used for the people in group 3 . Two notable conclusions from the study were: (1) patients receiving real or fake acupuncture experienced a greater reduction in pain than those receiving usual care; and (2) there was no significant difference in pain reduction between those who received real acupuncture (groups 2 and 3 ) and those who received fake acupuncture toothpick pokes.

For each of the statistical studies described indicate whether the study is an observational study or an experiment. Give a brief explanation for your choice. An article in USA Today (October 19,2010 ) describes a study of how young children learn. Sixty-four 18 -month-old toddlers participated in the study. The toddlers were allowed to play in a lab equipped with toys, which also had a robot hidden behind a screen. The article states: "After allowing the infants play time, the team removed the screen and let the children see the robot. In some tests, an adult talked to the robot and played with it. In others the adult ignored the robot. After the adult left the room, the robot beeped and then turned its head to look at a toy to the side of the infant. In cases where the adult had played with the robot, the infant was four times more likely to follow the robot's gaze to the toy."

Can moving their hands help children learn math? This is the question investigated by the authors of the paper "Gesturing Gives Children New Ideas about Math" (Psychological Science [2009]: \(267-272\) ). An experiment was conducted to compare two different methods for teaching children how to solve math problems of the form \(3+2+8=\ldots+8\). One method involved having students point to the \(3+2\) on the left side of the equal sign with one hand and then point to the blank on the right side of the equal sign before filling in the blank to complete the equation. The other method did not involve using these hand gestures. The paper states that the study used children ages 9 and 10 who were given a pretest containing six problems of the type described. Only children who answered all six questions incorrectly became subjects in the experiment. There were a total of 128 subjects. To compare the two methods, the 128 children were assigned at random to the two experimental conditions. Children in one group were taught a method that used hand gestures, and children in the other group were taught a similar strategy that did not involve hand gestures. Each child then took a test with six problems and received a score based on the number correct. From the resulting data, the researchers concluded that the average score for children who used hand gestures was significantly higher than the average score for children who did not use hand gestures. a. Answer the following seven questions for the experiment described above. (Hint: Reviewing Examples 1.5 and 1.6 might be helpful.) 1\. What question is the experiment trying to answer? 2\. What are the experimental conditions (treatments) for this experiment? 3\. What is the response variable? 4\. What are the experimental units and how were they selected? 5\. Does the design incorporate random assignment of experimental units to the different experimental conditions? If not, are there potentially confounding variables that would make it difficult to draw conclusions based on data from the experiment? 6\. Does the experiment incorporate a control group and/or a placebo group? If not, would the experiment be improved by including them? 7\. Does the experiment involve blinding? If not, would the experiment be improved by making it single- or double-blind? b. Based on the study design, do you think that the conclusions are reasonable?

The Institute of Psychiatry at Kings College London found that dealing with "infomania" has a temporary, but significant, negative effect on IQ (Discover, November 2005). To reach this conclusion, researchers divided volunteers into two groups. Each subject took an IQ test. One group had to check e-mail and respond to instant messages while taking the test, and the other group took the test without any distraction. The distracted group had an average score that was 10 points lower than the average for the control group. Explain why it is important that the researchers use random assignment to create the two experimental groups.

1.24 The hand-washing behavior of adults using public restrooms at airports was the subject of a study conducted by the American Society of Microbiology. A press release issued by the Society (September 15,2003 ) included the following description: Although illnesses as deadly as SARS and as troublesome as the common cold or gastric distress can be spread hand-to-hand, the survey sponsored by the American Society of Microbiology (ASM) found that many people passing through major U.S. airports don't wash their hands after using the public facilities. More than 30 percent of people using restrooms in New York airports, 19 percent of those in Miami's airport, and 27 percent of air travelers in Chicago aren't stopping to wash their hands. The survey, conducted by Wirthlin Worldwide in August 2003 , observed 7,541 people in public washrooms in New York, Chicago, San Francisco, Dallas, Miami, and Toronto. These results were then generalized to people who use public restrooms. Answer the following four questions for this observational study. (Hint: Reviewing Examples 1.3 and 1.4 might be helpful.) a. What is the population of interest? b. Was the sample selected in a reasonable way? c. Is the sample likely to be representative of the population of interest? d. Are there any obvious sources of bias?
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