Thanks everyone for your suggestions. I think that I'll be setting up the experiment such that the treatments are fully randomized, and that should prevent any systematic error and can be controlled as a residual variance, as Donald and Jos pointed out. I've also decided to take one treatment and repeat it (randomly, of course) throughout the experiment, and use that as a control. I can do a run test on those results to see if they're changing much, and if it can be rearranged with time and modelled, while I wouldn't use it to correct the other results because it may be specific to that treatment, I can note it in the discussion. That's the best I think I can do though, as far as measuring these changes in the water samples with time, since there is no specific measurement that I can take to see how they're changing and how it will affect the results of the experiment. Again, thanks for your help. If you have any other comments on the matter, I'd like to hear them. - Dave
[EMAIL PROTECTED] (Joe Ward) wrote in message news:<[EMAIL PROTECTED]>... > Dave -- > > If you "can't control it, then measure it" and include it in your model. > That's the VALUE of using RERESSION/LINEAR MODELS for your analyses. > > -- Joe > > ********************************** > Joe H. Ward, Jr. > 167 East Arrowhead Dr. > San Antonio, TX 78228-2402 > Phone: 210-433-6575 > Fax: 210-433-2828 > Email: [EMAIL PROTECTED] > http://www.northside.isd.tenet.edu/healthww/biostatistics/wardindex > ============================== > Health Careers High School > 4646 Hamilton Wolfe Road > San Antonio, TX 78229 > ********************************** > > > > . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
