1. Box and Whisker Plots or Boxplots

2. Variability and Skewness
Boxplots can be used to show:
Variability – high or low
Skewness – symmetric, skewed left, skewed right
Boxplots split the data into quarters (25%)
Use a five number summary to create the boxplot: :
Minimum value
1st quartile (Q1)
Median (2nd quartile or Q2)
3rd quartile (Q3)
The maximum value in a data set

3. Constructing a box and whisker plot
Example 1: Draw boxplot for the data
18, 27, 34, 52, 54, 59, 61, 68, 78, 82, 85, 87, 91, 93, 100
Find the 5 number summary:
Minimum value
1st quartile (Q1)
Median (2nd quartile or Q2)
3rd quartile (Q3)
The maximum value in a data set
Draw boxplot

4. Graphing The Data
Notice, the Box includes the lower quartile, median, and upper quartile.
The Whiskers extend from the Box to the max and min.
50% of data lies inside the box

5. Analyzing The Graph
Describe the variability:
Describe the skewness:

6. Practice
Example 2: The following are the scores of 12 members of a woman’s golf team.
89, 90, 87, 95, 86, 111, 85, 83, 88, 91, 79
Find the 5 number summary
Create a boxplot
The lowest 25% of the scores are below what value?
The middle 50% of the scores are between what numbers?
Half of the women scored better than what score?
Outliers?