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Yes, I don’t think it’s possible to observe a simpson’s paradox in a simple conversion test, either. Simpson’s paradox is about spurious correlations between v
by jameshart 3y ago
Yes, I don’t think it’s possible to observe a simpson’s paradox in a simple conversion test, either.
Simpson’s paradox is about spurious correlations between variables - conversion analysis is pure Bayesian probability.
It shouldn’t be possible to have a group as a whole increase its probability to convert, while having every subgroup decrease its probability to convert - the aggregate has to be an average of the subgroup changes.
- BoppreH 3y agoAre you sure? Consider the case where iOS users are more likely to convert than Android users, but you currently have very few iOS users. You then A/B test a new design that imitates iOS, but has awful copy. Both iOS and Android users are less likely to convert, but it attracts more iOS users. The group as a whole has higher conversion because of the demographic shift, but every subgroup has less.
- whimsicalism 3y agoI don't follow. If one bucket has many more iOS users, it seems like you have done a bad job randomizing your treatment?
- BoppreH 3y agoIt could be self-selection happening after you randomized the groups. For example a desktop landing page advertising an app, which might be installed on either mobile operating system.
- HWR_14 3y agoSimpson's paradox is sometimes about spurious correlations, but the original paradox Simpson wrote about was simply a binary question with 84 subgroups, where 3 or 4 subgroups with the outlying answer just had a significant enough amount of all samples, and a significant enough effect, to mutate the whole.