We saw a drop since September 7 and a spike on October 25 in the 7-day retention of Wikipedia iOS app users. We will start the investigation from the client side, since these changes happened within 7 days before a new release.
An example of how the 7-day retention is being computed: the 7-day retention of Sep 7 is the proportion of users who install the app on Sep 7 and open the app at least once on Sep 14.
The first step is to count the number of events for those suspicious date.


