This is Dataplot data file GRAYI617.DAT Visual Response & Contrast Study Source--Graybill & Iyer (1994). Regression Analysis: Concepts and Applications, Duxbury, page 617. Note--This data file GRA1617.DAT has equivalent contents to the Grabill-Iyer data file CONTRAST.DAT Response variable = proportion of times object seen (0 to 1) Number of observations = 10 Number of variables per line image = 2 Order of variables on a line image-- 1. Response variable = proportion of times object seen (0 to 1) 2. Factor 1 = foreground/background contrast Statistical category--Regression (non-linear) To read this file into Dataplot-- SKIP 25 READ GRAYI617.DAT Y X Proportion Contrast of Times Seen ---------------------------- .02 .000 .06 .005 .10 .010 .18 .015 .35 .020 .56 .025 .78 .030 .86 .035 .94 .040 .99 .045