Today I was advising my company that our various sites registration forms should have form labels above each field as opposed to using only in-field labels.
I explained that research has been conducted by many people to support this and cited the nielson groups page on the topic I even have had a user mention this in a recent user test. The user said that once the field was filled in it was hard to see what that field was during validation errors. And when distracted users have to return to fill in again and cannot tell what the field is.
So I advised labels above each field.
The reply I got from the marketing director was happy to test.
My question is, knowing that form labels are good idea to improve usabilty, should we AB test?
I know I could conduct another usability test but should we be doing either of these and eating into the limited UX budget when there is already so much research available to support the case for labels not being in-field only.
Is there a line you cross where you don't AB test every small usabilty improvement or should you infact test every small detail? Even previously proven ones?