GET
  FILE='C:\Documents and Settings\gillian raab\My Documents\aprojects\peas\web\exemp5\data\ex5wt.sav'.

*  Line above reads in the data. If you have opened ex5wt.sav  interactively you won't need to include it.
*---------------------------------------------------------------------------------------------------------------------------------------.
*logistic regression with grouped data in SPSS can only be done using PROBIT.
*Only the final model is shown here, although otehrs could have been tried.

*first compute interaction terms.
*---------------------------------------------------------------------------------------------------------------------------------------------.
compute agegrp2=agegrp*agegrp.
compute agesinc=agegrp*sinc.
compute sex=0.
if gender="F" sex=1.
compute agesex=agegrp*sex.
compute age2sex=agegrp2*sex.
execute.
*------------------------------------------------------------------------------------------------------------------------.
*  Now the logistic regression.
* needed extra iterations to converge.
*  this model is not quite the same as SAS since the agegp quadratic interaction with sinc.
* has been missed out.
* ------------------------------------------------------------------------------------------------------------------------..

PROBIT
  AyrA_num  OF npop  WITH sinc sacc  agegrp sex agegrp2  agesex age2sex agesinc
  /LOG NONE
  /MODEL LOGIT
  /CRITERIA ITERATE(50) STEPLIMIT(.1) .
*-------------------------------------------------------------------------------------

*The PROBIT command doesn't give predicted values in a file.
*although it has an option to print them out.
*so it is necessary to compute them from the output.
*--------------------------------------------------------------------------------------------------------- .
   compute lp= -4.47972-0.02489*sinc+sacc*0.04634+agegrp*(-0.00248)   +
    sex*.47620 + agegrp2  *(.00721)  +agesex*(-.00720) +age2sex*(-.00508)+agesinc*(.00152).  
compute phat=1/(1+exp(-lp)). 
compute gweight=1/phat.
execute. 
compute weighta=gweight/75.60964.