A ESCOLHA DO MÉTODO ESTATÃÂSTICO - SBPqO
A ESCOLHA DO MÉTODO ESTATÃÂSTICO - SBPqO
A ESCOLHA DO MÉTODO ESTATÃÂSTICO - SBPqO
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“We have discussed the practice of using different data<br />
transformations within a 2-way ANOVA with our statistical adviser and<br />
he stated that this is not valid, since the comparisons are not then<br />
between data of the same type. Transformation is performed to deal<br />
with 1 or more of 3 problems: non-normality, non-homogeneity of<br />
variance and non-additivity. To my understanding, in a 2-way analysis,<br />
'individualized' transformations, while solving the first two problems,<br />
would work against the third requirement of ANOVA, that treatment<br />
effects are additive. For instance, data in which treatment effect was<br />
multiplicative rather than additive are appropriately transformed to<br />
logs, since the treatment effects then become additive. But these<br />
could not then be compared with data that had not been transformed<br />
because they already fulfilled the ANOVA requirements. You would be<br />
comparing oranges and bananas.”<br />
“Sorry about the confusion induced by my last set of comments on<br />
the statistics. I think there might be still some sort of problem there, in<br />
that your comparison of the 30-min plaque solid data is on a<br />
somewhat different basis from the other comparisons. But I will<br />
discuss it when I next see our statistical advisor. I suspect that I put<br />
the question to him in a misleading way, combined with a misinterpretation<br />
of your analysis.”<br />
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