st: Calculating a "disagrement scale" from several individuall assessments

[Christer Thrane <lineea@broadpark.no>]

Hi,

I have three variables: A, B, and C. They are individual assesssments of the 
same phenomenon on a scale from 1 (poor) to 5 (very good). The data looks 
like:

id        A    B    C       DS
1        4    4     4        0
2        3    4     4        1
3        5    2     3        ?
4        2    2     4        ?
and so on.