Thank you everyone for your responses. To close this one off: IT WAS A CODING ERROR. IT IS NOT A BUG.
Took a while last night to find why this was happening. I tried to repeat a smaller model in excel with the troublesome variables and this resulted in some similar errors. So it is not a problem with PSPP and was obviously the data. Thank you all again. Happy Christmas Tim Goodspeed -----Original Message----- From: EKreyken <ekrey...@gmail.com> Sent: Wednesday, December 20, 2023 6:44 PM To: tim.goodsp...@btinternet.com Cc: pspp-users@gnu.org Subject: Re: dummy coding of categorical variables results in zero coefficients and standard errors Hi Time, Answering the stats stuff only: Without seeing the data, I can’t make a definitive call on this, but it seems that calculations for the t test cannot be completed properly. This indicates either a) no shared linear variability in your XY variables (incredibly rare to get perfect 0), forcing the t test to do a division of 0 over the variability in X, or b) your X variable has no variability (also incredibly rare), forcing the t test to divide shared linear variability over 0. You may have one of several problems. 1) dummy coding wasn’t done accurately and you don’t have enough variability in your X variable 2) you have a perfect non-relationship in those variables (very very rare) 3) you have a non-linear relationship that is really acting weird with the t-test, but it wouldn’t yield a n/a. Check the following: A) get the averages and standard deviations for all predictors. They should have a standard deviation above 0 for the test to work. B) plot the data for those specific predictors (X) against the response (Y) variable. You should end up with 2 separate graphs. Check for linear /non linear patterns. C) plot the residuals (google/youtube knows how to do this). Check for “randomness” vs patterns: patterns in the residuals are bad. If you’re interested, I offer stats consulting. Cheers, Elisabeth On Dec 20, 2023, at 1:47 AM, tim.goodsp...@btinternet.com wrote: found?
