Significant ≠ relevant [Design Issues]

posted by Astea – Russia, 2016-03-24 21:10 (3246 d 07:43 ago) – Posting: # 16137
Views: 24,418

Dear All!

I noticed it became fashionably for russian regulatories to ask to include group effect in the analyses even if in the protocal were stated the abovementioned rules. There are some more detailed situations when we were asked to take the effects into the ANOVA model. First is when the study is divided not only by groups by logystical reasons, but by groups by some other reasons (namely, different blood collection schemes). And the second is when there were drop-outs in the study and subjects were replaced by doubles (the date of the visit was to be included into the statistical model). I think that including term to ANOVA to prove it's significance is a bit naive because the true reasons may be various ("We shall see what we shall see"). What is your opinion on that topic?

And some practical questions:
  1. Which ANOVA model should be preffered in that cases Group, Group x Sequence or... ? (would be very grateful for link)?
  2. As I understand the residual variance depends on the quantity of terms (and even the more number of terms the less residual). Can we perform 2 different ANOVA models: first to exclude group effect, and second - to make a standard treatm+period+seq+sub(seq) calcaulation?
  3. What if we do get significant group term? Can we somehow make sure that number of subjects from only one group is sufficient for the study? What else can we take in such a case?

Grateful for your answers!

"Being in minority, even a minority of one, did not make you mad"

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