Indicators

[R A Bailey]

PJC said:
> 
> As I understand things (and I know I will be corrected if I am wrong):
> the reason that statisticians were interested in partial balance (in
> the association scheme form, and later in the Jordan algebra form)
> is that it eased the problem of inverting large matrices. Presumably
> this is less of an issue now: just throw them onto the computer.

This is part of the story.  Also relevant are that you know that pairs
in the same class have the same variance, and that for PBIBD(2)s
you have the intuitive result that greater concurrence implies smaller
variance, so that someone allocating real treatments to coded
treatments will probably do it right even they don't understand a lot
of theory.

RAB
-- 
R. A. Bailey
       
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