Statistical Procedures

Programming the statistical procedures from SAS
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didymo
Fluorite | Level 6

I have a repeated measures ANOVA Y=treatment year treatment*year but I am interested in two specific a priori contrasts.  Should I report the main effect treatment*year stats along with the a priori contrast stats or just the a priori contrast stats?  Thanks, BT

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SteveDenham
Jade | Level 19

Provided the a priori hypotheses are clearly stated, the only p values you need are those for the comparisons.  The stagewise procedure of looking at the Type III p value as a gateway to post hoc comparisons isn't needed.

 

SteveDenham

PS. A Bayesian analysis would make this more apparent.

didymo
Fluorite | Level 6

Thank you Steve.  However, in some cases if I explore Tukey's postdoc tests, then I would report type III p values of treatment year, and treatment*year as one would normally do, right?  

 

My knowledge of Bayesian stats is limited unfortunately. 

SteveDenham
Jade | Level 19

I agree.  If you do not have pre-planned comparisons, some form of adjustment for multiplicity should be done to control Type I error.

 

One of the advantages of Bayesian approaches is that since  the results do not have distributional or hypothesis assumptions and you can specify your utility (misclassification), you probably shouldn't be doing adjustments for multiplicity (per F. Harrell).

 

SteveDenham

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What is ANOVA?

ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.

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