Chi-Square Determinations

[CRMADDEN@wnp2.com]

     Some training material I was reviewing several years ago suggested that one 
     should not subtract background from source measurements made for chi-square 
     determinations.  It was stated that this would add a bias to the results. 
     I've not been able to locate a reference for this.
     
     Over the years, I have visited sites where background is subtracted and 
     some where it is not.
     
     Does anyone have any thoughts on this or a reference?
     
     Clay R. Madden
     Principal Health Physicist
     Washington Public Power Supply System
     CRMadden@WNP2.COM
     509/377-4460