ReferenceLineStyle

As of Version 8.0, ReferenceLineStyle is part of the built-in Wolfram Language kernel.

ReferenceLineStyle

is an option for QuantilePlot that specifies a style to use for the reference line.

Details and Options

To use ReferenceLineStyle, you first need to load the Statistical Plots Package using Needs["StatisticalPlots`"].
The reference line has a slope of unity.
If the points on the plot fall mostly on or near the reference line, the distributions are roughly the same.
Valid settings are None, Automatic, or a style or a list of styles. The default setting is Automatic.
With the setting ReferenceLineStyle->None, a reference line is not drawn.

QuantilePlot with a dashed reference line:

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