On 2 Jun 2004 17:27:03 -0700, [EMAIL PROTECTED] (Ray Koopman) wrote: > [EMAIL PROTECTED] (Anders D Hojen) wrote in message > news:<[EMAIL PROTECTED]>... > > [...] > > I'm measuring sentence durations to follow up studies on the seemingly > > trivial fact that non-native speakers tend to speak more slowly than > > native speakers. I'm trying to find the psycholinguistic locus (or loci) > > of their slowness. The hypothesis I'm testing is that that locus is > > syntactical processing. The between-groups factor is 'group' (native vs. > > non-native). The within-group factor is 'syntactic complexity' of the > > sentences that the subjects repeated (3 levels). > > > > In an ANOVA on the raw data, the interaction was significant, and I > > found that the mean group difference was not significant for the simple > > sentences, but for the complex sentences. Thus, I might infer that > > increased syntactic processing load slows non-native talkers down. > > > > However, syntactic complexity is confounded with sentence length, > > because the more complex the syntax of a sentence gets (i.e., the more > > words there are), the longer it inevitably gets. The group differences > > are larger for complex sentences (say, 2200 vs. 2500 ms) than simple > > sentences (say 500 vs. 550 ms). I'm wondering whether the ANOVA went: > > "Hey look, a delta of 300 is larger than a delta of 50; I'm gonna output > > a significant interaction". Will the ANOVA recognize that the delta of > > 50 is based smaller values than the delta of 300? This is why I thought > > of z-scores. But maybe they won't make a difference? > > [...] > > Try analyzing the logs of the durations. Then the anova, which always > looks at absolute differences in the numbers it has, will actually be > considering relative differences in the original numbers. And you may > also get rid of some of the interactions, too.
Taking the logs of the durations is an obvious thing. I believe it does not take special justification because a statistician should have recommended that before you began. As an alternative, re-stating the durations as time-per-word seems to me to be a realistic version of the outcome, which also might avoid interactions and heterogeneity of variances. -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html . . ================================================================ This list will soon be replaced by the new list EDSTAT-L at Penn State. Please subscribe to the new list using the web interface at http://lists.psu.edu/archives/edstat-l.html. ================================================================
