Section 113
Scatter Plots
A
scatter plot
can be used for data in the form of
ordered pairs
of numbers. The result will be a bunch of points "scattered" around the plane.
If the general tendency is for the points to rise to the right of the graph, then we say there is a
positive correlation
between the two variables measured. If the points fall to the left of the graph, we say there is
negative correlation
. If there is no general tendency, then there is
no correlation
.
If the tendency is not very pronounced  that is, the points are scattered widely  then we say the variables are
weakly correlated
. If the correlation is more pronounced, we say the variables are
strongly correlated
.

Weak positive correlation


Strong negative correlation


No correlation

Examples:

If you graphed a person's height on one axis and their weight on the other, you would probably get a strong positive correlation (because taller people generally weigh more).

If you graphed a man's age and the number of hairs on his head, you would probably get a weak negative correlation (because some men have a tendency for baldness as they get older).

If you graphed a woman's shoe size and the length of her hair, you would probably get no correlation. (These variables are unrelated.)