Chapter 1: Problem 79
To examine whether playing music in a store increases the amount customers spend, we randomly assign some stores to play music and some to stay silent and compare the average amount spent by customers.
Chapter 1: Problem 79
To examine whether playing music in a store increases the amount customers spend, we randomly assign some stores to play music and some to stay silent and compare the average amount spent by customers.
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Get started for freeEffects of Alcohol and Marijuana In 1986 the Federal Office of Road Safety in Australia conducted an experiment to assess the effects of alcohol and marijuana on mood and performance. \(^{29}\) Participants were volunteers who responded to advertisements for the study on two rock radio stations in Sydney. Each volunteer was given a randomly determined combination of the two drugs, then tested and observed. Is the sample likely representative of all Australians? Why or why not?
Do Cat Videos Improve Mood? As part of an "internet cat videos/photos" study, Dr. Jessica Gall Myrick posted an on-line survey to Facebook and Twitter asking a series of questions regarding how individuals felt before and after the last time they watched a cat video on the Internet. \(^{31}\) One of the goals of the study was to determine how watching cat videos affects an individual's energy and emotional state. People were asked to share the link, and everyone who clicked the link and completed the survey was included in the sample. More than 6,000 individuals completed the survey, and the study found that after watching a cat video people generally reported more energy, fewer negative emotions, and more positive emotions. (a) Would this be considered a simple random sample from a target population? Why or why not? (b) Ignoring sampling bias, what other ways could bias have been introduced into this study?
"Antibiotics in infancy may cause obesity in adults," claims a recent headline. \(^{49}\) A study in mice randomly assigned infant mice to either be given antibiotics or not, and the mice given antibiotics were more likely to be obese as adults. A separate study in humans found that children who had been given antibiotics before they were a year old (for example, for an ear infection) were more likely to be obese as adults. (Researchers believe the effect may be due to changes in the gut microbiome.) Based on these studies, is the headline an appropriate conclusion to make: (a) For mice? (b) For humans?
Canadians Stream Music In a random sample of 3500 Canadian consumers, about \(71 \%\) report that they regularly stream music. \(^{25}\) (a) Is the sample likely to be representative of all Canadian consumers? Why or why not? (b) Is it reasonable to generalize this result and estimate that about \(71 \%\) of all Canadian consumers regularly stream music?
Climate Change In July 2015, a poll asked a random sample of 1,236 registered voters in Iowa whether they agree or disagree that the world needs to do more to combat climate change. \({ }^{26}\) The results show that \(65 \%\) agree, while \(25 \%\) disagree and \(10 \%\) don't know. (a) What is the sample? What is the intended population? (b) Is it reasonable to generalize this result and estimate that \(65 \%\) of all registered voters in Iowa agree that the world needs to do more to combat climate change?
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