Chapter 4: Problem 24
Give two sets of five numbers that have the same mean but different standard deviations, and give two sets of five numbers that have the same standard deviation but different means.
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Chapter 4: Problem 24
Give two sets of five numbers that have the same mean but different standard deviations, and give two sets of five numbers that have the same standard deviation but different means.
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The amount of aluminum contamination (in parts per million) in plastic was determined for a sample of 26 plastic specimens, resulting in the following data ("The Log Normal Distribution for Modeling Quality Data When the Mean is Near Zero." Journal of Quality Technology \([1990]: 105-110)\) : \(\begin{array}{rrrrrrrrr}30 & 30 & 60 & 63 & 70 & 79 & 87 & 90 & 101 \\ 102 & 115 & 118 & 119 & 119 & 120 & 125 & 140 & 145 \\ 172 & 182 & 183 & 191 & 222 & 244 & 291 & 511 & \end{array}\) Construct a boxplot that shows outliers, and comment on the interesting features of this plot.
Consumer Reports Health (www.consumer reports.org/health) reported the sodium content \((\mathrm{mg})\) per 2 tablespoon serving for each of 11 different peanut butters: $$ \begin{array}{rrrrrrrr} 120 & 50 & 140 & 120 & 150 & 150 & 150 & 65 \\ 170 & 250 & 110 & & & & & \end{array} $$ a. Display these data using a dotplot. Comment on any unusual features of the plot. b. Compute the mean and median sodium content for the peanut butters in this sample. c The values of the mean and the median for this data set are similar. What aspect of the distribution of sodium content -as pictured in the dotplot from Part (a) - provides an explanation for why the values of the mean and median are similar?
Research by the Food and Drug Administration (FDA) shows that acrylamide (a possible cancer-causing substance) forms in high-carbohydrate foods cooked at high temperatures and that acrylamide levels can vary widely even within the same brand of food (Associated Press, December 6, 2002). FDA scientists analyzed McDonald's French fries purchased at seven different locations and found the following acrylamide levels: \(\begin{array}{lllllll}497 & 193 & 328 & 155 & 326 & 245 & 270\end{array}\) a. Compute the mean acrylamide level and the seven deviations from the mean. b. Verify that, except for the effect of rounding, the sum of the deviations from mean is equal to 0 for this data set. (If you rounded the sample mean or the deviations, your sum may not be exactly zero, but it should be close to zero if you have computed the deviations correctly.) c. Calculate the variance and standard deviation for this data set.
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.
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)?
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