

a small measured set-up error does
NOT
necessarily imply a small
problem
E(1) = 1 mm = s+r(1)
-14 -12 -10
14
-8 -6 -4 -2 0 2 4 6 8 10 12
s=1
r(1)=1
r(1)=-7
s=8
too simple off-line protocol:
measure day 1, correct on days 2,3,…
without new measurements, what to do in following fractions?