At 03:59 PM 2/20/02 -0300, Voltolini wrote: >Hi, > >I was reading a definition of "experiment" in science to be used in a >lecture and the use of treatments and controls are an important feature of >an experiment but.... my doubt is... is it possible to plan an experiment >without a control and call this as an "experiment" ? > >For example, in a polluted river basin there is a gradient of contamination >and someone are interested in to compare the fish diversity in ten rivers of >this basin. Then, the "pollution level" are the treatment (with ten levels) >but if there is not a clean river in the basin, I cannot use a control ! > >Is this an experiment anyway ?
the main issue is CONTROL OVER ... that the "experimenter" exerts over an independent variable if you want to compare diversity of fish ACROSS rivers ... and you find a difference, what does this necessarily have to do with contamination? i see three variables here ... diversity of fish ... rivers ... level of contamination (ie, where the gradients are different) what are you trying to show impacts on what? Dennis Roberts, 208 Cedar Bldg., University Park PA 16802 <Emailto: [EMAIL PROTECTED]> WWW: http://roberts.ed.psu.edu/users/droberts/drober~1.htm AC 8148632401 ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =================================================================
