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The article "Heartfelt Thanks to Fido" (San Luis Obispo Tribune, July 5,2003 ) summarized a study that appeared in the American Journal of Cardiology (March 15, 2003). In this study, researchers measured heart rate variability (a measure of the heart's ability to handle stress) in patients who had recovered from a heart attack. They found that heart rate variability was higher (which is good and means the heart can handle stress better) for those who owned a dog than for those who did not. a. Based on this study, is it reasonable to conclude that owning a dog causes higher heart rate variability? Explain. b. Is it reasonable to generalize the results of this study to all adult Americans? Explain why or why not.

Use the following information to answer. The paper "Turning to Learn: Screen Orientation and Reasoning from Small Devices" (Computers in Human Behavior [2011]\(: 793-797)\) describes a study that investigated whether cell phones with small screens are useful for gathering information. The researchers wondered if the ability to reason using information read on a small screen was affected by the screen orientation. The researchers assigned 33 undergraduate students who were enrolled in a psychology course at a large public university to one of two groups at random. One group read material that was displayed on a small screen in portrait orientation, and the other group read material on the same size screen but turned to display the information in landscape orientation (see the following figure). The researchers found that performance on a reasoning test based on the displayed material was better for the group that read material in the landscape orientation. Is the conclusion that reasoning using information displayed on a small screen is improved by turning the screen to landscape orientation appropriate, given the study design described above? Explain.

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/wine-news /montes-music-makes-wine-reach-parts-it-otherwise -couldnt-reach-82325/, retrieved April 8,2017 ). 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 concludedFor 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/wine-news /montes-music-makes-wine-reach-parts-it-otherwise -couldnt-reach-82325/, retrieved April 8,2017 ). 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 following statements, identify the number that appears in boldface type as the value of either a population characteristic or a statistic: a. A department store reports that \(84 \%\) of all customers who use the store's credit plan pay their bills on time. b. A sample of 100 students at a large university had a mean age of 24.1 years. c. The Department of Motor Vehicles reports that \(22 \%\) of all vehicles registered in a particular state are imports. d. A hospital reports that, based on the 10 most recent cases, the mean length of stay for surgical patients is \(\mathbf{6} . \mathbf{4}\) days. e. A consumer group, after testing 100 batteries of a certain brand, reported an average life of \(\mathbf{6 3}\) hours of use.

A petition with 500 signatures is submitted to a college's student council. The council president would like to determine what proportion of those who signed the petition are actually registered students at the college. There is not enough time to check all 500 names with the registrar, so the council president decides to select a simple random sample of 30 signatures. Describe the steps in a process she might use to do this.

In many digital environments, users are allowed to choose how they are represented visually online. Does the way in which people are represented online affectonline behavior? This question was examined by the authors of the paper "The Proteus Effect: The Effect of Transformed Self-Representation on Behavior" (Human Communication Research [2007]: 271-290). Participants were randomly assigned either an attractive avatar (a graphical image that represents a person) to represent them or an unattractive avatar. The researchers concluded that when interacting with a person of the opposite gender in an online virtual environment, those assigned an attractive avatar moved significantly closer to the other person than those who had been assigned an unattractive avatar. This difference was attributed to the attractiveness of the avatar. Explain why the researchers would not have been able to reach this conclusion if participants had been allowed to choose one of the two avatars (attractive, unattractive) themselves.

The article "Yes that Miley Cyrus Biography Helps Learning" (The Globe and Mail, August 5,2010 ) describes an experiment investigating whether providing summer reading books to low-income children would affect school performance. Subjects in the experiment were 1300 children randomly selected from first and second graders at low-income schools in Florida. A group of 852 of these children were selected at random from the group of 1300 participants to be in the book group. The other 478 children were assigned to the control group. Children in the book group were invited to a book fair in the spring to choose any 12 reading books that they could then take home. Children in the control group were not given any reading books, but were given some activity and puzzle books. These children received books each year for three years until the children reached third and fourth grade. The researchers then compared reading test scores of the two groups. a. Is randomly selecting 852 of the 1300 children to be in the book group is equivalent to random assignment of the two experimental conditions to subjects? Explain. b. Explain the purpose of including a control group in this experiment.

According to the article "Rubbing Hands Together Under Warm Air Dryers Can Counteract Bacteria Reduction" (Infectious Disease News, September 22,2010 ), washing your hands isn't enough-good "hand hygiene" also includes drying hands thoroughly. The article described an experiment to compare bacteria reduction for three different hand-drying methods. In this experiment, subjects handled uncooked chicken for 45 seconds, then washed their hands with a single squirt of soap for 60 seconds, and then used one of the three hand-drying methods. The bacteria count on their hands was then measured. Suppose you want to carry out a similar experiment with 30 subjects who are willing to participate. Describe the steps in a process you might use to randomly assign each of the 30 subjects to one of the hand-drying methods.

The article "Display of Health Risk Behaviors on MySpace by Adolescents" (Archives of Pediatrics and Adolescent Medicine [2009]: \(27-34\) ) described a study in which researchers looked at a random sample of 500 publicly accessible MySpace web profiles posted by 18-year-olds. The content of each profile was analyzed. One of the conclusions reported was that displaying sport or hobby involvement was associated with decreased references to risky behavior (sexual references or references to substance abuse or violence). a. Is it reasonable to generalize the stated conclusion to all 18-year-olds with a publicly accessible MySpace web profile? What aspect of the study supports your answer? b. Not all MySpace users have a publicly accessible profile. Is it reasonable to generalize the stated conclusion to all 18-year-old MySpace users? Explain. c. Is it reasonable to generalize the stated conclusion to all MySpace users with a publicly accessible profile? Explain.

The article "Rethinking Calcium Supplements" (U.S. Airways Magazine, October 2010) describes a study investigating whether taking calcium supplements increases the risk of heart attack. Consider the following four study descriptions. For each study, answer the following five questions: Question 1: Is the study described an observational study or an experiment? Question 2: Did the study use random selection from some population? Question 3: Did the study use random assignment to experimental groups? Question 4: Based on the study description, would it be reasonable to conclude that taking calcium supplements is the cause of the increased risk of heart attack? Question 5: Would it be reasonable to generalize conclusions from this study to some larger population? If so, what population? Study 1: Every heart attack patient and every patient admitted for an illness other than heart attack during the month of December, 2010 , at a large urban hospital was asked if he or she took calcium supplements. The proportion of heart attack patients who took calcium supplements was significantly higher than the proportion of patients admitted for other illnesses who took calcium supplements. Study 2: Two hundred people were randomly selected from a list of all people living in Minneapolis who receive Social Security. Each person in the sample was asked whether or not they took calcium supplements. These people were followed for 5 years, and whether or not they had had a heart attack during the 5-year period was noted. The proportion of heart attack victims in the group taking calcium supplements was significantly higher than the proportion of heart attack victims in the group not taking calcium supplements. Study 3: Two hundred people were randomly selected from a list of all people living in Minneapolis who receive Social Security. Each person was asked to participate in a statistical study, and all agreed to participate. Those who had no previous history of heart problems were instructed not to take calcium supplements. Those with a previous history of heart problems were instructed to take calcium supplements. The participants were followed for 5 years, and whether or not they had had a heart attack during the 5 -year period was noted. The proportion of heart attack victims in the calcium supplement group was significantly higher than the proportion of heart attack victims in the no calcium supplement group. Study 4: Four hundred people volunteered to participate in a 10-year study. Each volunteer was assigned at random to either group 1 or group \(2 .\) Those in group 1 took a daily calcium supplement. Those in group 2 did not take a calcium supplement. The proportion who suffered a heart attack during the 10 -year study period was noted for each group. The proportion of heart attack victims in group 1 was significantly higher than the proportion of heart attack victims in group 2