Posted by Larry Hoover on September 5, 2004, at 9:10:57
In reply to Re: Ecstasy safely converted and prescribed?, posted by SLS on September 5, 2004, at 8:19:54
> LOL
>
> These authors sometimes drive me nuts with their ambiguous wording. When I first read the following,
>
> "In healthy young men, the endogenous antioxidant defense system and a modest intake of dietary antioxidants are adequate to minimize levels of in vivo oxidant damage such that they cannot be differentiated by current methods."
>
> I took it to mean that the difference in measurments of oxidative damage between a normal diet and the one being studied could not be detected (differentiated).
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> Sometimes, they try to fit too many concepts in a single sentence. Just what the heck were they trying to say?
>
> I feel pretty silly.
>
>
> - ScottYou're not being silly at all. There is a presumption that they know what normal is in the first place. Most often, that means "typical". But typical may be something very different than "optimal". There are always assumptions. I am not satisfied by what is assumed to be normal, a priori.
The authors have found no evidence for the alternative hypothesis, and have therefore accepted the null. That does not preclude type 2 error. In fact, type 2 error is the harder of the two to avoid (alpha is an easier statistic to derive than is beta). They haven't *proven* there is no effect. They didn't *detect* one. Accepting the null hypothesis should not lead to any formal conclusion whatsoever, beyond a statement to that effect. It is a common error to imply that accepting the null is a rejection of the alternative. It is not.
In contrast, there are significant differences in oxidative stress and antioxidant parameters in dementia (compared to non-demented aging brains). The very existence of the word significant implies that alpha lies below an acceptable standard (>.05), and thus the data are probably meaningful. Just what they mean may be debated, but that is yet another matter.
Lar
poster:Larry Hoover
thread:383476
URL: http://www.dr-bob.org/babble/20040904/msgs/386610.html