10 a fire department in a rural county reports that

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10.A fire department in a rural county reports that its response time to fires is approximatelyNormally distributed with a mean of 22 minutes and a standard deviation of 11.9 minutes.Approximately what proportion of their response times is over 30 minutes?(a) 0.03(b) 0.21(c) 0.25(d) 0.75(e) 0.79
78The Practice of Statistics, 4/e- Chapter 2© 2011 BFW PublishersPart 2:Free ResponseShow all your work.Indicate clearly the methods you use, because you will be graded on thecorrectness of your methods as well as on the accuracy and completeness of your results andexplanations.The Dow Jones Industrial Average (―The Dow‖) is an index measuring the stock performance of30 large American companies, and is often used as a measure of overall economic growth in theUnited States.Below is Minitab output describing the daily percentage changes in the Dow forthe first three months of 2009 and the first three months of 2010.(Note that the market was openfor 61 days during the first three months of each year.A negative value indicates a percentagedecrease in the index for that day).Descriptive Statistics: Dow 2009, Dow 2010VariableNMeanStDevMinimumQ1MedianQ3Dow 200961-0.1982.331-4.600 -1.530-0.3101.150Dow 2010610.0780.821-2.640-0.2700.1100.465Both distributions are approximately Normally distributed.11.Consider a day when the Dow increased by 1%.In which year, 2009 or 2010, would such aday be considered a better day for the stock market, relative to other days in that year?Provide appropriate statistical calculations to support your answer.12.Based on these data, estimate how many of the 61 days in 2009 the Dowdecreasedby morethan 1%.13.Estimate the 19th percentile of daily change for the first three months of 2010.Maximum6.8201.660
© 2011 BFW PublishersThe Practice of Statistics, 4/e- Chapter 27914.―Normal‖ body temperature varies by time of day.A series of readings was taken of the bodytemperature of a subject.The mean reading was found to be 36.5°C with a standarddeviation of 0.3°C.If you wanted to convert the temperatures to the Fahrenheit scale, whatwould the new mean and standard deviation be?(Note:°F = °C(1.8) + 32).A local post office weighs outgoing mail and finds that the weights of first-class letters isapproximately Normally distributed with a mean of 0.69 ounces and a standard deviation of 0.16ounces.15.What is the 60thpercentile of first-class letter weights?16. First-class letters weighing more than 1 ounce require additional postage.What proportionof first-class letters at this post office require additional postage?17.Old-fashioned mechanical alarm clocks were not very accurate about when the alarm wentoff.The density curve below describes the distribution of times a certain alarm clock wentoff.The scale on thex-axis represents when the alarm went off, in seconds, before (negative)or after (positive) the alarm was set to go off.What proportion of the time did the alarm gooff within 10 seconds of the time it was set for?Shade the appropriate area on the graph toshow how you found the answer.

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