Erm, isn't it three times, or am I missing something?
You have what you are currently doing (feature Null), feature A, and feature B.
Otherwise, you can't distinguish that the feature is what is causing the change as opposed to something else like "novelty" (favoring a new feature) or "familiarity" (favoring an old feature).
If all you have is "what you are currently doing" as "feature A" and "new thing" as "feature B", you're going to have a murderous time getting enough statistical power to get any real information.
Erm, isn't it three times, or am I missing something?
You have what you are currently doing (feature Null), feature A, and feature B.
Otherwise, you can't distinguish that the feature is what is causing the change as opposed to something else like "novelty" (favoring a new feature) or "familiarity" (favoring an old feature).
If all you have is "what you are currently doing" as "feature A" and "new thing" as "feature B", you're going to have a murderous time getting enough statistical power to get any real information.