= Solution
Write $y_{WP}$ and $y_{AP}$ for the estimated <log odds ratios> relative to the common control. <Indirect treatment comparison> uses the consistency relation $\delta_{WA}=\delta_{WP}-\delta_{AP}$. For <independent> trials, subtraction adds their <variances>, giving
$$
\boxed{\widehat\delta_I=-1.95-(-0.69)=-1.26,\qquad v_I=0.15+0.10=0.25.}
$$
The substantive assumption is <transitivity in network meta-analysis>: the study populations, outcome definitions and follow-up are sufficiently comparable, particularly in their distributions of <effect modifiers>, that the two control comparisons estimate effects applicable to the same target population. The common control's name alone does not justify that assumption. This also assumes comparable marginal <odds ratios>; these need not equal covariate-adjusted <odds ratios> even without <confounding>.
Using the supplied rounded <variances> and the given <standard normal quantile>, the approximate <confidence interval> is
$$
\boxed{-1.26\pm2\sqrt{0.25}=(-2.26,-0.26).}
$$
On the <odds ratio> scale this is $e^{-1.26}\simeq0.284$, with approximate limits $(0.104,0.771)$. The estimated odds of recurrent stroke under treatment $W$ are about 28% of those under $A$, a reduction of about 72% in odds. The interval excludes equal odds, so this comparison provides evidence of lower odds under $W$ if the <indirect treatment comparison> assumptions hold. These are odds, not a 72% reduction in <probability>; a <confidence interval> describes the long-run coverage of the procedure, not a <posterior probability> for this particular interval.
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