文档介绍：Describing Data: Displaying and Exploring Data
Chapter 4
GOALS
Develop and interpret a dot plot.
Develop and inte 93, 94, 95, 96, and 97.
The stem value is the leading digit or digits, in this case 9. The leaves are the trailing digits. The stem is placed to the left of a vertical line and the leaf values to the right. The values in the 90 up to 100 class would appear as
Then, we sort the values within each stem from smallest to largest. Thus, the second row of the stem-and-leaf display would appear as follows:
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Stem-and-leaf: Another Example
Listed in Table 4–1 is the number of 30-second radio advertising spots purchased by each of the 45 members of the Greater Buffalo Automobile Dealers Association last year. Organize the data into a stem-and-leaf display. Around what values do the number of advertising spots tend to cluster? What is the fewest number of spots purchased by a dealer? The largest number purchased?
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Stem-and-leaf: Another Example
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Stem-and-leaf: Another Example (Minitab)
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The standard deviation is the most widely used measure of dispersion.
Alternative ways of describing spread of data include determining the location of values that divide a set of observations into equal parts.
These measures include quartiles, deciles, and percentiles.
Quartiles, Deciles and Percentiles
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To formalize the computational procedure, let Lp refer to the location of a desired percentile. So if we wanted to find the 33rd percentile we would use L33 and if we wanted the median, the 50th percentile, then L50.
The number of observations is n, so if we want to locate the median, its position is at (n + 1)/2, or we could write this as
(n + 1)(P/100), where P is the desired percentile.
Percentile Computation
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Percentiles - Example
Listed below are the commissions earned last month by a sample of 15 brokers at Salomon Smith Barney’s Oakland, California, office. Salomon Smith Barney is an investment company with offices located thro