To allow a cost-effectiveness analysis
based on a more meaningful interpretation
of the primary outcome measure, we also
compared the percentage of ‘improvers’ in
each group based on WAIS–III Digit Span
raw scores (improvers were defined as those
gaining 2 points or more on this measure
since baseline). This was based on a
relatively large effect size of 0.7 and was
chosen because recent studies suggest that
improvements of this size may contribute
to functional improvements (Bryson&Bell,
2003). For cost-effectiveness ratios based
on ‘improvers’, percentages were also compared
using non-parametric bootstrapping,
and were adjusted for baseline WAIS–III
Digit Span raw score and total PANSS
score.