[R] Clinical significance - Equivalence test

[David Winsemius]

On Mar 27, 2014, at 6:53 AM, Manuel Carona wrote:

> Hi,
> 
> I have implemented a therapeutic intervention on two groups (one is a
> control group) and tested them in two moments using some assessment
> tools (with normative data). Now I want to compare the experimental
> group with the control group using clinical equivalence testing. To do
> this I need to specify a range of closeness (One for each assessment
> tool according to the specificity of this same tool) and do two
> one-tailed tests to test if the two groups are considered clinically
> equivalent in the first moment and on the end I want to compare the
> experimental group with the normative data (Here I have to add the mean
> and standard deviation of the normative sample because I don't have the
> normative sample).
> 
> I know that R has a package named equivalence but I don't know how to do
> this kind of calculations with it. Is it even possible with the actual
> packages?

It sounds as though you need to be seeking statistical consultation first. You have multiple measures over multiple times and have not yet clearly articulated the meaning of "equivalence" in this setting. What if one measure shows a small non-equivalent result and another measure shows a bigger difference? What if the differences are in opposite directions? You need to pre-specify whether the bigger difference wins or whether the two measures are additive or exactly what the final standard for evaluation might be BEFORE you do the data analysis. This _should_ have been conducted before gathering data, but failing that it now needs to be defined before any statistical testing.

-- 
David.

> 
> Thanks in advance
> 
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David Winsemius
Alameda, CA, USA