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the data points move ‘‘upward-and-to-the-right’’ along a perfectly-fitting straight
line (see Fig. 6.1 ).
Fig. 6.1
Example of a scatterplot for a perfect, positive correlation (r = +1.0)
Figure 6.2 shows the scatterplot for a moderately positive correlation of
r = +0.53. This means that each x-value can predict each y-value moderately well
because you can draw a picture of a ‘‘football’’ around the outside of the data
points that move upward-and-to-the-right, but not along a straight line (see
Fig. 6.2 ).
Fig. 6.2
Example of a scatterplot for a moderate, positive correlation (r = +0.53)
Figure 6.3 shows the scatterplot for a low, positive correlation of r = +0.23.
This means that each x-value is a poor predictor of each y-value because the
‘‘picture’’ you could draw around the outside of the data points approaches a circle
in shape (see Fig. 6.3 ).
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