Chapter 4: Problem 10
Consider the following statement: More than \(65 \%\) of the residents of Los Angeles earn less than the average wage for that city. Could this statement be correct? If so, how? If not, why not?
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Chapter 4: Problem 10
Consider the following statement: More than \(65 \%\) of the residents of Los Angeles earn less than the average wage for that city. Could this statement be correct? If so, how? If not, why not?
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A sample of concrete specimens of a certain type is selected, and the compressive strength of each specimen is determined. The mean and standard deviation are calculated as \(\bar{x}=3000\) and \(s=500\), and the sample histogram is found to be well approximated by a normal curve. a. Approximately what percentage of the sample observations are between 2500 and \(3500 ?\) b. Approximately what percentage of sample observations are outside the interval from 2000 to 4000 ? c. What can be said about the approximate percentage of observations between 2000 and \(2500 ?\) d. Why would you not use Chebyshev's Rule to answer the questions posed in Parts (a)-(c)?
The paper 'Relationship Between Blood Lead and Blood Pressure Among Whites and African Americans" (a technical report published by Tulane University School of Public Health and Tropical Medicine, 2000 ) gave summary quantities for blood lead level (in micrograms per deciliter) for a sample of whites and a sample of African Americans. Data consistent with the given summary quantities follow: \(\begin{array}{lrllrrrl}\text { Whites } & 8.3 & 0.9 & 2.9 & 5.6 & 5.8 & 5.4 & 1.2 \\ & 1.0 & 1.4 & 2.1 & 1.3 & 5.3 & 8.8 & 6.6 \\ & 5.2 & 3.0 & 2.9 & 2.7 & 6.7 & 3.2 & \\ \text { African } & 4.8 & 1.4 & 0.9 & 10.8 & 2.4 & 0.4 & 5.0 \\\ \text { Americans } & 5.4 & 6.1 & 2.9 & 5.0 & 2.1 & 7.5 & 3.4 \\ & 13.8 & 1.4 & 3.5 & 3.3 & 14.8 & 3.7 & \end{array}\) a. Compute the values of the mean and the median for blood lead level for the sample of African Americans. Which of the mean or the median is larger? What characteristic of the data set explains the relative values of the mean and the median? b. Construct a comparative boxplot for blood lead level for the two samples. Write a few sentences comparing the blood lead level distributions for the two samples.
Bidri is a popular and traditional art form in India. Bidri articles (bowls, vessels, and so on) are made by casting from an alloy containing primarily zinc along with some copper. Consider the following observations on copper content \((\%)\) for a sample of Bidri artifacts in London's Victoria and Albert Museum ("Enigmas of Bidri," Surface Engineering [2005]: 333-339), listed in increasing order: \(\begin{array}{llllllllll}2.0 & 2.4 & 2.5 & 2.6 & 2.6 & 2.7 & 2.7 & 2.8 & 3.0 & 3.1 \\ 3.2 & 3.3 & 3.3 & 3.4 & 3.4 & 3.6 & 3.6 & 3.6 & 3.6 & 3.7\end{array}\) \(\begin{array}{llllll}4.4 & 4.6 & 4.7 & 4.8 & 5.3 & 10.1\end{array}\) a. Construct a dotplot for these data. b. Calculate the mean and median copper content. c. Will an \(8 \%\) trimmed mean be larger or smaller than the mean for this data set? Explain your reasoning.
Mobile homes are tightly constructed for energy conservation. This can lead to a buildup of indoor pollutants. The paper "A Survey of Nitrogen Dioxide Levels Inside Mobile Homes" (Journal of the Air Pollution Control Association \([1988]: 647-651\) ) discussed various aspects of NO, concentration in these structures. a. In one sample of mobile homes in the Los Angeles area, the mean \(\mathrm{NO}_{2}\) concentration in kitchens during the summer was \(36.92 \mathrm{ppb}\), and the standard deviation was 11.34. Making no assumptions about the shape of the \(\mathrm{NO}_{2}\) distribution, what can be said about the percentage of observations between \(14.24\) and \(59.60 ?\) b. Inside what interval is it guaranteed that at least \(89 \%\) of the concentration observations will lie? c. In a sample of non-Los Angeles mobile homes, the average kitchen \(\mathrm{NO}_{2}\) concentration during the winter was \(24.76 \mathrm{ppb}\), and the standard deviation was \(17.20 .\) Do these values suggest that the histogram of sample observations did not closely resemble a normal curve? (Hint: What is \(\bar{x}-2 s ?\)
The ministry of Health and Long-Term Care in Ontario, Canada, publishes information on its web site (www.health.gov.on.ca) on the time that patients must wait for various medical procedures. For two cardiac procedures completed in fall of 2005 the following information was provided: a. The median wait time for angioplasty is greater than the median wait time for bypass surgery but the mean wait time is shorter for angioplasty than for bypass surgery. What does this suggest about the distribution of wait times for these two procedures? b. Is it possible that another medical procedure might have a median wait time that is greater than the time reported for "90\% completed within"? Explain.
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