A topic is what your paper is about; a purpose is what you want to change in a particular reader, and only the second one can succeed or fail. Assemble a purpose statement from the four dropdowns and watch the testability report react — then take the register dial and calibrate the same idea to four different rooms.
1 · Build a purpose statement
Topic
Action verb — what do you want to do to someone?
Reader — who, specifically?
The change — so that they…
The means — by…
This sentence rarely appears in the finished text. It lives at the top of your working file, where it stops you wandering into an interesting paragraph that serves no one.
3 · Register dial
Formality
SlangyCasualPlainFormalInflated
Rooms judged correctly0 / 0
2 · Is it testable?
4 · How it reads at this setting
Plain professionalregister 3 of 5
Casual register is not incorrect English. It is English calibrated for a different setting — and the failure mode is never informality, it is mismatch, in either direction.