2. Chapter 3: Averages and Variation Section 4: Percentiles and Box- and-Whisker Plots

3. Measure of Position Describes how a data value relates to the other data in a collection of data values.

4. Percentiles The mth percentile is the number that separates the bottom m% of the data from the top (100 – m)% of the data. denoted P m

5. Quartiles Divide data into quarters The first quartile Q 1 = P 25 The second quartile Q 2 = P 50 (median) The third quartile Q 3 = P 75

6. Interquartile Range resistant measure of dispersion IQR = Q 3 - Q 1

7. Box-and-Whisker Plots sometimes called box plots used to display graphic and numerical features of collections of data created using 5 numbers: lowest data value, highest data value and the three quartiles, Q 1, Q 2, and Q 3

8. Example Construct a boxplot for the following data values. 1 2 2 3 3 3 4 5 7 7 9 10 14 20 29 42

9. Example 0 45 1 3 6 12 42