Editing Analysis of covariance (section)

===Adjusting preexisting differences===
Another use of ANCOVA is to adjust for preexisting differences in nonequivalent (intact) groups. This controversial application aims at correcting for initial group differences (prior to group assignment) that exists on DV among several intact groups. In this situation, participants cannot be made equal through random assignment, so CVs are used to adjust scores and make participants more similar than without the CV. However, even with the use of covariates, there are no statistical techniques that can equate unequal groups. Furthermore, the CV may be so intimately related to the categorical IV that removing the variance on the DV associated with the CV would remove considerable variance on the DV, rendering the results meaningless.<ref>{{cite journal |last1=Miller |first1=G. A. |last2=Chapman |first2=J. P. |year=2001 |title=Misunderstanding Analysis of Covariance |journal=Journal of Abnormal Psychology |volume=110 |issue=1 |pages=40–48 |doi=10.1037/0021-843X.110.1.40 |pmid=11261398 }}</ref>