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The Desirability of Covariance Adjustments
Author(s) -
Abeyasekera S.
Publication year - 1984
Publication title -
journal of the royal statistical society: series c (applied statistics)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.205
H-Index - 72
eISSN - 1467-9876
pISSN - 0035-9254
DOI - 10.2307/2347660
Subject(s) - covariance , econometrics , environmental science , statistics , mathematics
SUMMARY The decision on whether or not to adjust the estimate of the difference between the effects of two treatments according to the value of a covariate is investigated by a simulation study. Two criteria for deciding whether or not to adjust are compared. Adjustment is recommended unless it is known that the covariate is very poorly correlated with the response variable or there is a serious lack of degrees of freedom for estimating the regression coefficient of the response variable on the covariate value. The reasons for this are discussed.