Line of Best Fit
Age
(months)
18
19
20
21
22
23
24
25
26
27
28
29
Height
(inches)
76.1
77
78.1
78.8
79.7
79.9
81.1
81.2
82.8
83.5
Work with your group
to make a prediction
for the height at:
• 21 months
• 28 months
• 20 years
Line of Best Fit
• Definition - A Line of Best is a straight line on
a Scatterplot that comes closest to all of the
dots on the graph.
• A Line of Best Fit does not touch all of the
dots.
• A Line of Best Fit is useful because it allows
us to:
– Understand the type and strength of the
relationship between two sets of data
– Predict missing Y values for given X values, or
missing X values for given Y values
Equation For Line of Best Fit
y = 0.6618x + 64.399
X (months)
Formula
Y (inches)
21
0.6618(21) + 64.399
78.3
28
0.6618(28) + 64.399
82.9
240
0.6618(240) + 64.399
223.3
Predicting Data with
Scatterplots
• Interpretation - Making a prediction for an
unknown Y value based on a given X value
within a range of known data
• Extrapolation - Making a prediction for an
unknown Y value based on a given X value
outside of a range of known data
• More accurate: Interpretation
• Less accurate: Extrapolation