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ERIC Number: ED342791
Record Type: Non-Journal
Publication Date: 1992-Feb
Pages: 17
Abstractor: N/A
Reference Count: N/A
The Homogeneity of Regression Assumption in the Analysis of Covariance.
Bump, Wren M.
An analysis of covariance (ANCOVA) is done to correct for chance differences that occur when subjects are assigned randomly to treatment groups. When properly used, this correction results in adjustment of the group means for pre-existing differences caused by sampling error and reduction of the size of the error variance of the analysis. The adjustment of the means is done to reduce bias that may be caused by the differences. This hoped-for increase in power is a major advantage of ANCOVA. However, the inappropriate use of ANCOVA appears to be the rule rather than the exception. This paper explains the homogeneity of regression assumption and why it is so important to evaluate this assumption before conducting an ANCOVA. Small heuristic data sets (3 groups of 12 entries each for intelligence quotient and achievement) are used to make the discussion concrete. Three tables present the data sets, and five figures illustrate their application. A seven-item list of references is included. (SLD)
Publication Type: Speeches/Meeting Papers
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A