GIGO

Many people have heard the expression **"Garbage In
-- Garbage Out"** -- which is not too surprising an expression.
However there are two other sayings that can be associated with the letters GIGO
that you might not have thought about before....

**"Genius In -- Garbage Out"** can happen
when we take good information (genius might be too strong a word, but you get
the idea), combine that information with other 'good' information, but in ways
that mathematically meaningless. For example, averaging ordinal numbers
(such as 4 for an 'A' in a graduate course, 3 for a 'B', etc. is
mathematically meaningless and the resulting average can be considered 'garbage'
even though the letter grades were well thought out and appropriate evaluations
of a student's performance. As another example, using some 'mathematical
model' that does not adequately represent reality can produce 'garbage' results
even though input to the model might be good. As another example,
experiments have shown that weights and scores spreadsheets to evaluate choice
alternatives produce inadequate results because people who might be well versed
in the decision, cannot 'assign' weights for the importance of the criteria
accurately enough.

**"Garbage In -- Genius Out" **might seem
like magic, but we can convert
ordinal pairwise comparisons to
ratio scale priorities using AHP verbal
comparisons provided we have enough redundancy and variety. Whereas
ordinal measures cannot be used in arithmetic operations such as addition and
multiplication, ratio scale numbers can and so we can produce measures with a
higher level of meaning by computing the principle right hand
eigenvector of a set of
pairwise verbal judgments.