# An exit poll is conducted by surveying everyone who

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Chapter 13 / Exercise 2
Seeing Through Statistics
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An exit poll is conducted by surveying everyone who leaves the polling booth at 50 ran- domly selected election precincts. What type of sampling is being used? (random, stratified, systematic, cluster, convenience) d. A manufacturer makes fertilizer sticks to be used for growing plants. A manager finds that the amounts of fertilizer placed in the sticks are not very consistent, so that for some fertiliza- tion lasts longer than claimed, while others don’t last long enough. She wants to improve qual- ity by making the amounts of fertilizer more consistent. When analyzing the amounts of fer- tilizer, which of the following statistics is most relevant: mean, median, mode, midrange, standard deviation, first quartile, third quartile? Should the value of that statistic be raised, lowered, or left unchanged? 7. Sampling Shortly after the World Trade Center towers were destroyed, America Onlineran a poll of its Internet subscribers and asked this question: “Should the World Trade Centertowers be rebuilt?” Among the 1,304,240 responses, 768,731 answered “yes,” 286,756 an-swered “no,” and 248,753 said that it was “too soon to decide.” Given that this sample is ex-tremely large, can the responses be considered to be representative of the population of theUnited States? Explain. 8. Sampling What is a simple random sample? What is a voluntary response sample? Whichof those two samples is generally better? 9. Observational Study and Experiment What is the difference between an observa-tional study and an experiment? 10. Histogram What is the major flaw in the histogram (in the margin) of the outcomes of100 rolls of a fair die?
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Chapter 13 / Exercise 2
Seeing Through Statistics
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From Data to Decision133INTERNETPROJECTUsing Statistics to Summarize DataGo to The importance of statistics as a tool to summa-rize data cannot be underestimated. For example,consider data sets such as the ages of all the stu-dents at your school or the annual incomes ofevery person in the United States. On paper,these data sets would be lengthy lists of num-bers, too lengthy to be absorbed and interpretedon their own. In the previous chapter, you learneda variety of graphical tools used to representsuch data sets. This chapter focused on the useof numbers or statistics to summarize various as-pects of data.Just as important as being able to summarizedata with statistics is the ability to interpretsuchstatistics when presented. Given a number suchas the arithmetic mean, you need not only to un-derstand what it is telling you about the underly-ing data, but also what additional statistics youneed to put the value of the mean in context.The Internet Project for this chapter will helpyou develop these skills using data from such di-verse fields as meteorology, entertainment, andhealth. You will also discover uses for such statis-tics as the geometric mean that you might nothave expected.The CD included with this book contains applets de-signed to help visualize various concepts. Open theApplets folder on the CD and click on Start.Selectthe menu item of Mean versus median.Create a setof points that are very close together and then add apoint that is far away from the others. What is the ef-fect of the new point on the mean? What is the effectof the new point on the median? Also, create a dataset with a median below 2 and a mean between 2and 4.FROM DATA TO DECISIONThe From Data to Decisionproject atthe end of Chapter 2 listed the ages ofactresses and actors at the times thatthey won Oscars in the Best Actress andBest Actor categories. Refer to thosesame ages.Critical ThinkingUse methods from this chapter to com-pare the two data sets. Are there differ-ences between the ages of the Best Ac-tresses and the ages of the Best Actors?