> > If the treatment is successful, will it be utilised in future? If so, > then I don't think you can honestly say that the children in the study are > the only ones of interest (i.e., the population). They are a sample from > a population that includes future children, and so the population variance > is not really known. I'd use t-tests rather than z-tests. > > You may also want to set your per-contrast alpha lower than the usual .05 > in order to keep the family-wise alpha at a reasonable level. For a nice > demonstration of this issue, see Jerry Dallal's Little Handbook of > Statistical practice (http://www.tufts.edu/~gdallal/LHSP.HTM), and click > on the link for A Valuable Lesson > (http://www.tufts.edu/~gdallal/multtest.htm).
I'm currently just concerned with whether the pre-treatment scores of those in control group, and those in the treatment group are ths same. So for this exercise, isn't it true to say that I have data for the entire population of interest, and therefore sigma is known? Many Thanks, Don (alias Eircom) . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
