I am often requested to repost my five commandments.  These are
 posted here without exegesis.

 For the client:

         1.  Thou shalt know that thou must make assumptions.

         2.  Thou shalt not believe thy assumptions.

 For the consultant:

         3.  Thou shalt not make thy client's assumptions for him.

         4.  Thou shalt inform thy client of the consequences
             of his assumptions.

 For the person who is both (e. g., a biostatistician or psychometrician):

         5.  Thou shalt keep thy roles distinct, lest thou violate
             some of the other commandments.



The consultant is obligated to point out how their assumptions affect
their views of their domain; this is in the 4-th commandment.  But the
consultant should be very careful in the assumption-making process not
to intrude beyond possibly pointing out that certain assumptions make
large differences, while others do not.  A good example here is regression
analysis, where often normality has little effect, but the linearity of
the model is of great importance.  Thus, it is very important for the
client to have to justify transformations.

There are, unfortunately, many fields in which much of the activity 
consists of using statistical procedures without regard for any assumptions.