On Thu, 20 Mar 2003 21:10:37 GMT, Syrahz Derzai <[EMAIL PROTECTED]> wrote:
> Rich Ulrich <[EMAIL PROTECTED]> wrote: > > On 19 Mar 2003 10:58:15 -0800, [EMAIL PROTECTED] (dennis roberts) wrote: > > > for the above statement you are suggesting that the p value gives you > > > information on the "strength" of evidence for the possible fact that the > > > effect is NOT absolutely 0 ... > > > > No, no, no. You don't have to invent your naive straw-man for > > what I was "suggesting", since I was explicit in my NEXT line. > > > > "- the strength of the evidence? Whether *chance* > > might be sufficient to account for what has been observed?" > > > > Not 'the fact that the effect is NOT absolutely 0'. > > But > > 'whether the occurrence is unlikely by chance.' > > But then it requires a leap of faith to attribute observations to > something else rather than chance merely because it is "unlikely by > chance". Yes and No. Controlled studies are set up precisely so that we can attribute something-in-particular. Study manipulations are not always perfectly "blind" to participants and to raters, etc., but the randomization removes the most notorious of the outside influences. - That is, there are certain biases that scientists do know about; so it is poor practice to ignore them, if there is way we know to do better. (And we do have to take into account the new problems that we might learn about.) Certainly, in non-controlled studies, there's a 'leap of faith' -- What is it that connects the hypothesize item to the outcome, besides some number? That's why an education leading to research needs to emphasize the philosophical roots. 'Correlation is not causation.' The better scientists are the ones who know this in their bones, so they are more careful to describe and account for whatever else might exist. Then, as Herman might say, there is a decision to make -- What are the consequences? Sometimes, there is mainly an up-side in plunking for slight evidence, or very little evidence at all. (But this branches into wider, metaphysical issues, so I will stop here.) -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
