DDFM - What does DDFM stand for? The Free Dictionary
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The degrees of freedom were calculated according to the Satterthwaite (= DDFM
Analyses were performed using PROC MIXED of SAS (SAS Institute, 1999), with error terms and denominator degrees of freedom being specified using the DDFM
= SATTERTH option.
option on the model statement in MIXED procedure was used to specifiy containment, Satterthwaite or Kenward Roger approaches for determining fixed effects and degrees of freedom.
Tests of significance of fixed effects were accomplished by combining the appropriate linear combination of mean squares utilizing Satterthwaite's (Satterthwaite, 1946) approximation using the DDFM
= SATTERTH option with the MODEL statement in PROC MIXED.
Error terms and denominator degrees of freedom were specified by the DDFM
= SATTERTH option in the model statement of PROC MIXED, and specific pairs of treatment differences were compared by the LSMEANS PDIFF option.