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Concept: Box-and-Whisker Plots
A box-and-whisker plot is a visual representation of how the data is spread out and how much variation there is. The main advantage of the box-and-whisker plot is that it is not cluttered by showing all the data values. It highlights only a few important features of the data. Therefore, the box-and-whisker plot makes it easier to focus attention on the median, extremes, and quartiles and comparisons among them. Another advantage of the box-and-whisker plot is that it does not become more complicated with more data values. A disadvantage of the box-and-whisker plot occurs when there are only a few data values.
Constructing a box-and-whisker plot:
First, arrange the data in the table above in increasing order.
46, 46, 51, 52, 54, 58
60, 64, 69, 70, 74, 74
Seventh, draw a rectangular box extending from the lower quartile to the upper quartile. Indicate the median with a vertical line extending through the box.
Eighth, connect the lower extreme toto the lower quartile with a line (one "whisker") and the upper quartile to the upper extreme with another line (the other "whisker".)
Repeat steps one through eight to construct box-and-whisker plots using the data given for San Antonio and New York, respectively.
If there are an odd number of data values, the overall median is not included among the values used to calculate the medians of the lower or upper quartiles.
Example: 13 19 20 21 23 23 23 24 25 25 26 26 28
Direct comments to: firstname.lastname@example.org