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Illustration of a Technique Which Tests Whether Two Regression Lines Are Parallel When the Variances Are Unequal

Potthoff, Richard F.
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
United States Air Force Office of Scientific Research, Hypothesis Testing, Regression (Statistics), Statistical Analysis


It may be desired to test the hypothesis that two regression lines are parallel without assuming that the variances of the two sets of error terms are necessarily equal. This paper presents a relatively non-technical discussion of a test which can be used for this situation. A numerical illustration is included. The test statistic used is analogous to the well-known Wilcoxon statistic. This paper is intended for the practitioner rather than for the theoretician; the more technical aspects of the test are covered in a separate paper (RB-62-29).

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