Chapter 3: Averages and Variation Section 4: Percentiles and Box- and-Whisker Plots.
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Transcript of Chapter 3: Averages and Variation Section 4: Percentiles and Box- and-Whisker Plots.
Chapter 3: Averages and Variation
Section 4: Percentiles and Box-and-Whisker Plots
Measure of Position
• Describes how a data value relates to the other data in a collection of data values.
Percentiles
• The mth percentile is the number that separates the bottom m% of the data from the top (100 – m)% of the data.
• denoted Pm
Quartiles
• Divide data into quarters
• The first quartile Q1 = P25
• The second quartile Q2 = P50 (median)
• The third quartile Q3 = P75
Interquartile Range
• resistant measure of dispersion
• IQR = Q3 - Q1
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, Q1, Q2, and Q3
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
Example
0
45
13
6
12
42