Re: [bug #48040] GLM produces wrong output

[John Darrington]

I think I have fixed this problem now.

Could you please try it out?

J'

On Fri, May 27, 2016 at 12:11:20PM -0500, Alan Mead wrote:
     On 5/27/2016 11:24 AM, John Darrington wrote:
     > Follow-up Comment #1, bug #48040 (project pspp):
     >
     > Thanks for the bug report.
     >
     > PSPP (unlike SPSS) does not show the "intercept" if the model is
     > unbalanced, since it has no meaning (just what calculation SPSS does in 
this
     > case is a mystery).
     
     
     The intercept has never been of interest to me, so I don't have much
     experience. However, I thought the intercept was simply the value of the
     dependent variable when the composite of independent variables was
     zero?  Being unbalanced prevents the composite of independent variables
     from having a zero point? Or am I misunderstanding?
     
     By "unbalanced" do you mean that some cells are entirely missing? Or
     that cells and not all the same size? (Both of which are true in these
     data.)
     
     > The negative F value (and consequently NaN df) are more of a concern, 
possibly
     > also related to missing values.
     
     From the output, it's possible this is all (or much) of the issue is due
     to the df being calculated wrong.  The error df somehow came out
     negative, which caused the error MS to be negative, which caused all the
     F's to be negative.
     
     Although that explanation doesn't explain how the second analysis failed
     to find significant main effects for both independent variables.
     
     Also it's interesting that the total SS match between PSPP and SPSS
     precisely in both analyses, but the error SS are off by a bit in the
     first analysis (where things went really wrong).
     
     > Also the speed issues concern me too.
     
     Possibly a windows issue as I cannot replicate on the same/comparable
     hardware running Linux. PSPP becomes unresponsive when running this
     analysis (i.e., in response to mouse events, Windows adds "(Not
     Responding)" to the title bar--a sign that usually means that the
     application is crashing or fallen into an infinite loop or some similar
     failure).  I was surprised when the output appeared while I was
     preparing the bug report.
     
     -Alan
     
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