  This report answers queries about extending the blinding index approach to a
situation with measurements at multiple time points. The key question is how to
test if there is progressive unblinding. A related question is how to apportion
extent of unblinding between primary cause (trial design) and secondary cause
(AE or efficacy).
  It is indeed possible to answer these questions. Sections 2 to 5 develop the
narrative. Section 6 addresses the basic question about testing for progressive
unblinding. The strategy is to use various statistical methods available in
literature. One method is generalized McNemar test for marginal homogeneity.
Second is a weighted least squares approach described by Stokes et al (2000).
Third is application of polytomous logistic regression. Fourth and last is a
simulation approach. This is the key part of the report. Other questions are
answered in Section 7. Numerical illustrations are given based on hypothetical
data (since a trial is yet to be conducted). Relevant program code is available
if needed.
