Have an idea?

Visit Sawtooth Software Feedback to share your ideas on how we can improve our products.

HB Reg - First Part Worth Utility Removed

I understand the first part worth utility is removed to zero center the results and save degrees of freedom/ensure independence like it is in CBC/HB.  However, in CBC/HB the results file contains values for each parameter, even if they have been removed/zero-centered in the analysis.  For HB-Reg (which I am relatively new to), the Point Estimates.csv doesn't provide any results for the first parameter of each variable.  

Am I simply supposed to calculate it myself by taking the negative sum of the remaining part worths for that parameter?

Or am I missing something more important?

asked Aug 18, 2014 by Joel Anderson Bronze (1,585 points)
Yes, just like if you were using any general estimation routine under Excel, SPSS, or SAS, you just need to fill in the reference parameter by computing it.  If dummy coding, the reference level per attribute is zero.  If effects-coding, the reference parameter is negative the sum of the other levels withint that same attribute.

1 Answer

+1 vote

The first level is removed to avoid multicollinearity issues but the centering of the utilities depends on the coding method.  In CBC/HB we use effects coding by default which will zero-center the utilities.  However in HB-Reg, the coding is dummy coding.  Thus the value for the first level is assumed to be zero.
answered Aug 18, 2014 by Walter Williams Gold Sawtooth Software, Inc. (22,155 points)