Red and yellow creates orange. Yellow and blue creates green. The secondary colors can be mixed further to create additional shades. Tertiary colors are the result of a primary and secondary color mixed together. For example, orange mixed with red creates red-orange.
An influential point is an outlier that greatly affects the slope of the regression line. One way to test the influence of an outlier is to compute the regression equation with and without the outlier. This type of analysis is illustrated below.
Usually, the presence of an outlier indicates some sort of problem. This can be a case which does not fit the model under study, or an error in measurement. Outliers are often easy to spot in histograms. For example, the point on the far left in the above figure is an outlier. A convenient definition of a outlier is a point which falls more than 1.5 times the interquartile range above the third quartile or below the first quartile. Outliers can also occur when comparing relationships between two sets of data.