Subject: within-subject comparisons in psychoacoustics From: Chris Chambers <Chris.Chambers(at)SCI.MONASH.EDU.AU> Date: Fri, 27 Oct 2000 16:30:39 +1100Hello, I would like to pose a question to the readers of this group on the pros and cons of doing within-subject analyses. Those of us who researching psychoacoustics are well aware of the tradition in which individuals are tested extensively and individual trends in the data are reported rather than groups effects. Sometimes ANOVAs and t-tests are conducted on individual subjects to see if the treatment effect signficantly influenced performance for *that* subject. However, often, particularly for instance for research on psychophysical tuning curves, such statistics are not reported. From consulting with statisticians, I have learned that one problem with determining statistical significance of within-subject comparisons is that ANOVA and t-tests require that data-points within each condition are statistically independent. If all the data in a particular analysis are provided by one subject then it can be argued that individual data points within each treatment are no longer independent, and hence not amenable to ANOVA. I would be very interested in hearing from other researchers who have encountered this problem in their experiments and the various approaches you may have taken to deal with it. I would especially like to hear the views of those who have conducted significance tests on within-subject comparisons and the justifications you have for doing so in light of this apparent violation of the assumptions of ANOVA. Best, Chris -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Chris Chambers Department of Psychology Monash University Clayton, Victoria 3168 AUSTRALIA Tel. +61 3 9905 3978 Fax. +61 3 9905 3948 EMAIL: chris.chambers(at)sci.monash.edu.au -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-