There’s a great App Promotion Summit presentation (video) at Vimeo, by Simon Kendall of Adeven, on app analytics. He covers what to track, ensuring you have comparable KPIs and explains cohort analysis.
I was particularly interested in the part where Simon explained that it’s important that you are comparing things that can be compared. For example, what exactly is a session? Is a session necessarily the same across say Android and iOS? It actually depends on how it is measured.
If a new session is taken to be whenever the app comes to the foreground then this can vary depending on whether the phone has lots of notifications coming in and how often the user context switches in and out of the app to see other things such as notifications, sms, use social media or make a call. It turns out coming to foreground isn’t a great measure for a session. This varies too much across users and across OS platforms. Instead you should define a session as one separated from other sessions by a suitable time, say 30 mins. In fact, this is how sessions are defined for traditional web sites.
View the presentation to gain more insights and also learn about cohort analysis where you group users by a particular criteria, for example time of install, so that their actions are more comparable and easier to analyse for patterns.
Also take a look at other App Promotion Summit videos that contains a large number of insights on app marketing.