TY - JOUR
T1 - Power and Measures of Effect Size in Analysis of Variance with Fixed Versus Random Nested Factors
AU - Siemer, Matthias
AU - Joormann, Jutta
PY - 2003/12/1
Y1 - 2003/12/1
N2 - Ignoring a nested factor can influence the validity of statistical decisions about treatment effectiveness. Previous discussions have centered on consequences of ignoring nested factors versus treating them as random factors on Type I errors and measures of effect size (B. E. Wampold & R. C. Serlin, 2000). The authors (a) discuss circumstances under which the treatment of nested provider effects as fixed as opposed to random is appropriate; (b) present 2 formulas for the correct estimation of effect sizes when nested factors are fixed; (c) present the results of Monte Carlo simulations of the consequences of treating providers as fixed versus random on effect size estimates, Type I error rates, and power; and (d) discuss implications of mistaken considerations of provider effects for the study of differential treatment effects in psychotherapy research.
AB - Ignoring a nested factor can influence the validity of statistical decisions about treatment effectiveness. Previous discussions have centered on consequences of ignoring nested factors versus treating them as random factors on Type I errors and measures of effect size (B. E. Wampold & R. C. Serlin, 2000). The authors (a) discuss circumstances under which the treatment of nested provider effects as fixed as opposed to random is appropriate; (b) present 2 formulas for the correct estimation of effect sizes when nested factors are fixed; (c) present the results of Monte Carlo simulations of the consequences of treating providers as fixed versus random on effect size estimates, Type I error rates, and power; and (d) discuss implications of mistaken considerations of provider effects for the study of differential treatment effects in psychotherapy research.
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U2 - 10.1037/1082-989X.8.4.497
DO - 10.1037/1082-989X.8.4.497
M3 - Article
C2 - 14664685
AN - SCOPUS:0346199347
VL - 8
SP - 497
EP - 517
JO - Psychological Methods
JF - Psychological Methods
SN - 1082-989X
IS - 4
ER -