# Influential Observations in a Scatter Diagram

- Author:
- David Gurney

- Topic:
- Statistics

Last updated 2/4/2019

Move the seed value to select a new set of data.
Move the class slider to choose a different number of classes.
If you move point A or point B, up or down, notice how the
regression line follows. If you move point C up or down,
the regression line does not move so much.
This is why points A and B are called influential observations.
When you move A and B, they have a large influence on the
regression line. Since moving point C has a much smaller
effect on the regression line, point C is NOT an influential
observation.
Notice that there are large horizontal gaps between points
A and B and the rest of the data points. These large
horizontal gaps are what cause the points A and B to be
influential observations.

Influential observations are worth pointing out in a scatter
diagram since they have a big influence on where the
regression line is located. Because of their influence,
the coordinates of influential outliers should be checked.
Updated November 13, 2013.