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When
to Use a Scatter Diagram
Use a Scatter Diagram to
determine if there is correlation between two characteristics. Correlation
implies that as one variable changes, the other also changes. Although this
may indicate a cause and effect relationship, this is not always the case,
since there may be a third characteristic (or many more) that are actually
the cause, and both the characteristics of interest are the effect.
Sometimes, though, if
we know that there is good correlation between two characteristics, we can
use one to predict the other, particularly if one characteristic is easy
to measure and the other isn't. For instance, if we prove that weight gain
in the first trimester of pregnancy correlates well with fetus development,
we can use weight gain as a predictor. The alternative would be expensive
tests to monitor the actual development of the fetus.
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