Study Guide and Intervention (continued) - MathnMind

13-5
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Study Guide and Intervention
Box-and-Whisker Plots
Box-and-Whisker Plots A box-and-whisker plot displays the extremes, the quartiles,
and the median for a set of data. The length of the box represents the interquartile range. A
vertical line inside the box represents the median. Horizontal lines (whiskers) represent the
lower and upper fourths of the data. The bullets at each end are the extreme values.
Example
Draw a box-and-whisker plot for the following data.
3, 7, 9, 14, 16, 19, 19, 25, 28
Step 1 Determine the quartiles and any outliers.
With the data ordered from least to greatest, determine the quartiles.
7 9
The median is 16. The lower quartile, Q1 , is or 8. The upper quartile,
2
19 25
Q3 , is or 22.
2
The interquartile range is 22 8 14.
Check to see if there are any outliers. An outlier is a data value that is at least
1.5 interquartile ranges less than Q1 or greater than Q3 .
8 1.5(14) 13 and 22 1.5(14) 43
There are no numbers less than 13 or greater than 43 in the data set. Therefore,
there are no outliers.
Step 2 Draw and label a number line. Use a scale that includes the extreme values.
0 3 6 9 12 15 18 21 24 27 30
Step 3 Complete the box-and-whisker plot. Draw a box to designate the data between the
upper and lower quartiles. Draw a line through the median. Draw a line from the
lower quartile to the least value and from the upper quartile to the greatest value.
0
Exercises
3
Q2 M 16
Q1 8 Q3 22
6
9 12 15 18 21 24 27 30
Draw a box-and-whisker plot for each set of data.
1. 19, 49, 73, 30, 32, 46, 51, 30 2. 8, 2, 4, 2, 9, 13, 2, 5, 19, 24, 13, 1
0 10 20 30 40 50 60 70 80
3. 51, 55, 59, 20, 62, 48, 45, 44, 41, 71 4. 14.2, 15.3, 18.1, 16.5, 17.8, 17.5, 20.1,
15.8, 16.5, 17.9, 18.1, 19.0
0 10 20 30 40 50 60 70 80
0 4 8 12 16 20 24 28 32
13 14 15 16 17 18 19 20 21
© Glencoe/McGraw-Hill 805 Glencoe Algebra 1
Lesson 13-5