Yes! Thanks for putting this all in words. I'm really bad at putting things
in writing so I appreciate this even more.

On Thursday, December 10, 2015, Kevin Smith <[email protected]> wrote:

> Excellent summary. Please make sure this is on wiki as well.
>
> Thanks
>
> Kevin
> On Dec 10, 2015 8:05 AM, "Oliver Keyes" <[email protected]
> <javascript:_e(%7B%7D,'cvml','[email protected]');>> wrote:
>
>> Totally unrelated to my previous email, I promise. This is just me
>> writing down my thinking on how A/B testing works, and how it applies
>> to the portal (www.wikipedia.org) experiments and the schema we have
>> deployed there.
>>
>> A/B testing is a common way of identifying if a proposed change to a
>> piece of software is actually an improvement or not: it consists of
>> taking a sample of users and dividing them into two groups, the "A"
>> and "B" groups (hence the name). One group is consistently given the
>> experimental change (the "test" group). One group is consistently
>> given the default experience (the "control" group). Users are
>> pseudorandomly sorted into each group, so that both groups are even.
>> The end outcome for both groups is compared, and the change is
>> successful if users in the test group are statistically significantly
>> more likely to experience a better outcome than the users in the
>> control group.
>>
>> When we put together the schema for the Portal we did it after months
>> of experimenting with the Cirrus A/B tests, which means that we tried
>> to structure it to take into account the lessons we learned there. We
>> discovered that things were simpler the more fields you had; that
>> maintaining a base population who were not participating in any tests
>> was ideal for dashboarding. Accordingly the schema tracks every KPI we
>> care about for the portal and contains a "cohort" field that indicates
>> if someone is in the "A" group, the "B" group, or no group whatsoever
>> - with the idea that most users at any one time would be in /no/ group
>> and we could rely on that population for dashboarding! That way we can
>> handle everything with one schema.
>>
>> So the things to remember when setting up Portal tests:
>>
>> 1. The test and control groups should be even;
>> 2. The test and control group should (together) make up a very small
>> chunk of the total people getting the logging. 10% combined, say.
>> 3. The test and control group should both be represented with "cohort"
>> values, with nothing (to produce a MySQL NULL) for the rest of the
>> population.
>>
>> That way we can both test and dashboard simultaneously.
>>
>> --
>> Oliver Keyes
>> Count Logula
>> Wikimedia Foundation
>>
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