Microsoft Office Tutorials and References

In Depth Information

Fig. 6.5
Example of a Scatterplot for a Moderate, Negative Correlation (r

¼
─

.39)

Fig. 6.6
Example of a Scatterplot for a Perfect, Negative Correlation (r
¼
─
1.0)

Fig.
6.5
). In this case, it is a negative correlation because the “football” you could

draw around the data points slopes down and to the right.

Fig.
6.6
shows a perfect negative correlation of
r

1.0
which means that X is

a perfect predictor of Y, although in an inverse relationship such that as X increases,

Y decreases. The data points ﬁt perfectly along a downward-sloping straight line

(see Fig.
6.6
)

Let’s explain the formula for computing the correlation
r
so that you can

understand where the number summarizing the correlation came from.

In order to help you to understand
where
the correlation number that ranges from

¼
─

þ

─

1.0 comes from, we will walk you through the steps involved to use the

formula as if you were using a pocket calculator. This is the one time in this topic

1.0 to

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