Which are the target devices for the study?

A website might be targeted at both large-screen and small-screen devices; a product might only offer a companion app for iPhones, and so on. These requirements must be documented and taken into consideration when recruiting the participants.

When testing websites, an additional question to ask is which browsers and browser versions are relevant; when testing apps, it's relevant to understand what ratio of smartphone operating systems reflect the actual customer base and should thus be covered. Study sponsors will always say that the app versions for the various smartphone operating systems are identical, but this is not always true. If the versions are significantly different, the UX researcher will have to create separate studies, because the discussion guides/scripts will necessarily be different, too.