Ch 9
Regression Wisdom
Mrs Johnson
AP Statistics
What to watch out for:
O Make sure the data is straight
O Check the Residual Plots
O Scattered above and below with no apparent
pattern
O No major gaps or outliers
O Look for subsets in your data that might
need to be looked at separately
What to watch out for:
O Extrapolation
O It is rarely a good idea to go beyond the limits
of your data set to make predictions for
values.
O Stay within your data set
O Data points that could be considered
outliers, have strong leverage or be
influential points
Outliers
O Can be an outlier in the x direction or the y
direction
O Can be influential points –if you remove
point, does slope change?
O Can be points with LARGE residual or SMALL
residual - distance from LSLR
O Can be points that have large leverage or
small leverage – think of leverage in terms
of a moment arm… (i.e. x is far from x-bar)
Leverage – High/Low?
Influential point – Yes/No?
Residual – Large/Small?
What would
happen to
correlation if r
was removed?
r would get closer
to positive one
AS the scatter
decreases
Leverage – High/Low?
Influential point – Yes/No?
Residual – Large/Small?
?
What would
happen to
correlation if r
was removed?
r would get closer
to positive one
AS the scatter
decreases
Leverage – High/Low?
Influential point – Yes/No?
Residual – Large/Small?
?
What would
happen to
correlation if r
was removed?
r would get
SLIGHTLY less
positive as the
scatter would
increase
Leverage – High/Low?
Influential point – Yes/No?
Residual – Large/Small?
?
What would
happen to
correlation if r
was removed?
r would get closer
to 1 as the
scatter would
decrease
Life Expectancy – Ch 9 #24
Country
Births/W Life
oman
Expect
Country
Births/W Life
oman
Expect
Argentina
2.5
77
Guatemala
4.7
68
Bahamas
2.2
77
Honduras
4.0
72
Barbados
1.8
78
Jamaica
2.5
77
Belize
3.5
74
Mexico
2.8
75
Bolivia
4
64
Nicaragua
3.6
71
Brazil
2.2
71
Panama
2.5
76
Canada
1.5
82
Paraguay
4
72
Chile
2.2
79
Peru
3.1
71
Colombia
2.7
74
Puerto Rico
3.1
71
Costa Rica
25
79
US
2.1
80
Dom. Rep
2.8
73
Uruguay
2.3
78
Ecuador
3.1
71
Venezuela
2.9
76
El Salvador
3.2
72
Virgin
Islands
2.4
79
Complete the following:
O Create a scatterplot
O Is the line an
and describe
association
O Any countries that
seem to not fit
pattern?
O Find correlation and
interpret R2
O Find LSLR
appropriate model?
O Interpret slope and yintercept
O If government
leaders want to
increase life
expectancy, should
they encourage
women to have fewer
children?