thanx for the tip - didn't realise there was a syntax. cheers
Emma Kylie Lange <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>... > Further to Donald's comments about investigating the nature of the > dependent-covariate interaction is the Johnson-Neyman technique for > calculating the region of significance. This will tell you at what > cut-points the regression slopes of your treatment groups change from being > not significantly different to significant. > > This then allows you to put values on the regions that Donald described > where group A > group B, group A < group B etc. > > There is SPSS syntax for the J-P technique available at > http://support.spss.com/answernet/details.asp?ID=19193 which in turn was > developed from SAS code (reference given). > > Kylie. > > > Donald Burrill wrote: > > > If the lines meet, or cross, (or even if they come close to meeting), > > then there is a range of values of the covariate for which the groups do > > not differ (in the general vicinity of the meeting point; this may be > > more complicated to describe, but will be easy enough to see, if you > > have more than two groups, since nobody can guarantee that the meeting > > point for lines A and B is anywhere near the meeting point for lines B > > and C, etc.). > > > > If the lines do cross (some of them, anyway), then there are probably > > regions of the covariate for which > > group A > group B, group A < group B, and group A = group B > > approximately (in the sense of "no significant difference"). . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
