Determining Degree of Covariance, rik
Øu(xi,xk) = u(xi)u(xk)rik 
for -1<rik<1
for -1<rik<1ØPrevious tests
lWith enough data can calculate rik for a particular
test/situation
ØAnalytical
ØExperience
lCan make an educated guess about value of r