Chapter 3: Problem 38
Can the standard deviation have a negative value? Explain.
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Chapter 3: Problem 38
Can the standard deviation have a negative value? Explain.
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Nixon Corporation manufactures computer monitors. The following data give the numbers of computer monitors produced at the company for a sample of 30 days. \(\begin{array}{llllllllll}24 & 32 & 27 & 23 & 33 & 33 & 29 & 25 & 23 & 36 \\\ 26 & 26 & 31 & 20 & 27 & 33 & 27 & 23 & 28 & 29 \\ 31 & 35 & 34 & 22 & 37 & 28 & 23 & 35 & 31 & 43\end{array}\) a. Calculate the values of the three quartiles and the interquartile range. Where does the value of 31 lie in relation to these quartiles? b. Find the (approximate) value of the 65 th percentile. Give a brief interpretation of this percentile. c. For what percentage of the days was the number of computer monitors produced 32 or higher? Answer by finding the percentile rank of 32 .
A large population has a bell-shaped distribution with a mean of 310 and a standard deviation of 37 . Using the empirical rule, find what percentage of the observations fall in the intervals \(\mu \pm 1 \sigma, \mu \pm 2 \sigma\), and \(\mu \pm 3 \sigma\).
According to the American Time Use Survey conducted by the Bureau of Labor Statistics (www.bls.gov/atus/), Americans spent an average of \(985.50\) hours watching television in \(2010 .\) Suppose that the standard deviation of the distribution of times that Americans spent watching television in 2010 is \(285.20\) hours. a. Using Chebyshev's theorem, find at least what percentage of Americans watched television in 2010 for i. \(272.50\) to \(1698.50\) hours ii. \(129.90\) to \(1841.10\) hours *b. Using Chebyshev's theorem, find the interval that contains the time (in hours) that at least \(75 \%\) of Americans spent watching television in 2010 .
The lengths (in seconds) of the eight most recent songs played on \(98.9\) FM WCLZ and WCLZ.com (Portland, ME) at \(1: 28\) p.m. on Wednesday July 20,2011 were as follows: \(\begin{array}{llllllll}251 & 252 & 213 & 182 & 244 & 259 & 262 & 216\end{array}\) Calculate the range, variance, and standard deviation.
The following data give the prices (in thousands of dollars) of 20 houses sold recently in a city. 1 3 \(\begin{array}{llllllllll}184 & 297 & 365 & 309 & 245 & 387 & 369 & 438 & 195 & 390 \\ 323 & 578 & 410 & 679 & 307 & 271 & 457 & 795 & 259 & 590\end{array}\) Find the \(20 \%\) trimmed mean for this data set.
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