4.4 OUTLIERS AND DOT
PLOTS
WHAT IS AN OUTLIER?
• Sometimes, distributions are
characterized by extreme values
that differ greatly from the other
observations. These extreme
values are called outliers.
HOW DO YOU KNOW IF A DATA POINT
IS AN OUTLIER?
LOWER BOUNDARY
UPPER BOUNDARY
< 𝑸𝟏 − 𝟏. 𝟓(𝑰𝑸𝑹)
> 𝑸𝟑 + 𝟏. 𝟓(𝑰𝑸𝑹)
• EX 1: 16, 19, 20, 24, 28
• EX 2: 49, 65, 58, 46
• Would 3 be an outlier?
• Would 5 be an outlier?
• Would 80 be an outlier?
• Would 84 be an outlier?
WHAT DO OUTLIERS LOOK LIKE ON A
BOX PLOT?
BOX PLOTS USED IN THE MEDICAL
FIELD!
CREATE A BOX PLOT AND DETERMINE:
•
•
•
•
•
•
Min
Q1
MED
Q3
Max
Outlier Boundaries (lower and upper)
• 16, 22, 19, 18, 12, 10, 17, 14, 18, 21, 16, 20, 20
DOTPLOT
Advantages
Disadvantages
• See every data point
• Quickly see the range
(highest and lowest
point)
• Easy to see the mode
(most frequent data
point)
• Takes a long time to
construct if many data
points
Dot Plot
Collection 1
40
50
60
70
Test_Grades
80
90
100
CREATING A DOT PLOT
• Create a dot plot for the following data:
52, 43, 61, 69, 69, 55, 62, 52, 47, 54, 69, 43, 53,48
STEM AND LEAF PLOTS
The Stem-and-Leaf Plot is a type of graph where the
data is arranged by place value. The digits in the
largest place are referred to as the stem and the
digits in the smallest place are referred to as the leaf
(leaves). The leaves are displayed to the right of the
stem. Stem and Leaf Plots are great organizers for
large amounts of information.
CREATING STEM AND LEAF PLOTS
• 15, 16, 21, 23, 23, 26,
26, 30, 32, 41
• 126, 106, 95, 114, 98,
107, 114, 128, 134,
117, 122, 129