Note: The Z score is computed in order to identify significant changes in the degree of
compliance overtime, for example, the change in compliance from 1998 to 1999 can be
calculated by the above formula. In this case, sample group 1 is 1998 and sample group 2
is 1999. When making calculation of changes from 1999 to 2000, sample group 1 is 1999
and sample group 2 is 2000