Critique of enhanced power claimed for Quasi-ANCOVA and Dual-Centered ANCOVA.
other · Level V
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- Record sourced from PubMed, PMID 39841649.
- Also identified by DOI 10.1371/journal.pone.0317860 and PMC identifier 11753683.
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Abstract
Two related methods, Quasi-ANCOVA and Dual-Centered ANCOVA, have recently been suggested as a way to get greater power when analyzing data from a before and after study. Both methods use group-mean centering where the groups are the treatment and comparison groups. Group-mean centering creates a generated regressor problem. When the estimated standard errors are corrected for the generated regressor problem, there is no longer any gain in power. The corrected Quasi-ANCOVA estimates are identical to those from ANOVA and the corrected Dual-Centered ANCOVA estimates are identical to those from the differences model. These conclusions are derived analytically and also verified using a Monte Carlo simulation.