Hi Chris Take a look at this weblnk:
http://r-eco-evo.blogspot.com/2011/08/comparing-two-regression-slopes-by.html Comparing two regression lines (slopes) by means of an ANCOVA (in Ecology). For Analysis of Covariance (ANCOVA) to compare regression lines look at: http://udel.edu/~mcdonald/statancova.html Hope this helps. Ling Ling Huang Sacramento City College --- On Tue, 3/20/12, Chris Lortie <lor...@yorku.ca> wrote: From: Chris Lortie <lor...@yorku.ca> Subject: [ECOLOG-L] how to compare two fitted lines To: ECOLOG-L@LISTSERV.UMD.EDU Date: Tuesday, March 20, 2012, 11:21 AM hi Ecolog, I was wondering if anyone had any good how-to references on comparing fitted lines. Here is what I usually do, particularly if there is one x and two y's paired. 1. Save predicted values from fit line and do a t-test on the two arrays. 2. Save residuals and examine patterns between fit models. 3. Include confidence intervals for fit lines, and they don't overlap, the lines are different. 4. Use resampling to examine the likelihood that these two fit lines would emerge from a population of points. 5. Take difference between every pair of response points (provided share independent variable), and use a t-test to determine if the mean is different from 0. Is there a best/preferred or standard approach that use in ecology? cheers, chris lortie.
