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Chapter 5: Bivariate Data
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If the pattern is linear, does the pattern or association slope upwards or
slope downwards?
Are the plotted values tightly clustered together in the pattern or widely
separated?
Are there noticeable deviations from the pattern?
Notes:
Two variables are said to be positively related if larger values of one
variable tend to be associated with larger values of the other.
Two variables are said to be negatively related if larger values of one
variable tend to be associated with smaller values of the other.
Observe that the scatter plots presented in
Figure 5-2
through
Figure 5-7
display different patterns and associations. In
Figure 5-2
, the variables are
positively related since larger values of the dependent
y
variable are
associated with larger values of the independent
x
variable, and vice versa.
The values are all located on a straight line with a positive slope, and
therefore one can say that there is a
perfect positive linear association
between the two variables. Perfect linear positive association rarely occurs
when sample data are collected.