Hi On 20 Feb 2002, Voltolini wrote: > 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 ?
As others have indicated this would not be an experiment in the narrow sense of the term because you are not experimentally manipulating the independent variable (i.e., degree of pollution). So this would be a non-experimental study (sometimes called correlational studies, although that use confounds design and analysis issues). However, I remember some statistics books that used the term experiment to refer to any situation in which numbers are assigned to objects of study, thus incorporating all of statistics into the analysis of such "experimental" data. This use would accommodate both manipulated (i.e., true experimental) and measured (i.e., non-experimental) factors. Best wishes Jim ============================================================================ James M. Clark (204) 786-9757 Department of Psychology (204) 774-4134 Fax University of Winnipeg 4L05D Winnipeg, Manitoba R3B 2E9 [EMAIL PROTECTED] CANADA http://www.uwinnipeg.ca/~clark ============================================================================ ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =================================================================
