Chapter 3: Problem 1
Explain how the value of the median is determined for a data set that contains an odd number of observations and for a data set that contains an even number of observations.
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Chapter 3: Problem 1
Explain how the value of the median is determined for a data set that contains an odd number of observations and for a data set that contains an even number of observations.
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When studying phenomena such as inflation or population changes that involve periodic increases or decreases, the geometric mean is used to find the average change over the entire period under study. To calculate the geometric mean of a sequence of \(n\) values \(x_{1}, x_{2}, \ldots, x_{n}\), we multiply them together and then find the \(n\) th root of this product. Thus $$ \text { Geometric mean }=\sqrt[n]{x_{1} \cdot x_{2} \cdot x_{3} \cdot \ldots \cdot x_{n}} $$ Suppose that the inflation rates for the last five years are \(4 \%, 3 \%, 5 \%, 6 \%\), and \(8 \%\), respectively. Thus at the end of the first year, the price index will be \(1.04\) times the price index at the beginning of the year, and so on. Find the mean rate of inflation over the 5 -year period by finding the geometric mean of the data set \(1.04,1.03,1.05,1.06\), and \(1.08 .\) (Hint: Here, \(n=5, x_{1}=1.04, x_{2}=1.03\), and so on. Use the \(x^{1 / n}\) key on your calculator to find the fifth root. Note that the mean inflation rate will be obtained by subtracting 1 from the geometric mean.)
Suppose that on a certain section of I-95 with a posted speed limit of \(65 \mathrm{mph}\), the speeds of all vehicles have a bell-shaped distribution with a mean of \(72 \mathrm{mph}\) and a standard deviation of \(3 \mathrm{mph}\). a. Using the empirical rule, find the percentage of vehicles with the following speeds on this section of I-95. i. 63 to \(81 \mathrm{mph}\) ii. 69 to \(75 \mathrm{mph}\) *b. Using the empirical rule, find the interval that contains the speeds of \(95 \%\) of vehicles traveling on this section of \(\mathrm{I}-95\).
Refer to Exercise \(3.115\). Suppose the times taken to learn the basics of this word processor by all students have a bell-shaped distribution with a mean of 200 minutes and a standard deviation of 20 minutes. a. Using the empirical rule, find the percentage of students who will learn the basics of this word processor in i. 180 to 220 minutes ii. 160 to 240 minutes "b. Using the empirical rule, find the interval that contains the time taken by \(99.7 \%\) of all students to learn this word processor.
Can the standard deviation have a negative value? Explain.
Following are the temperatures (in degrees Fahrenheit) observed during eight wintry days in a midwestern city: \(\begin{array}{llllllll}23 & 14 & 6 & -7 & -2 & 11 & 16 & 19\end{array}\) Compute the range, variance, and standard deviation.
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