[Apple Roof Cleaning]

Roof Cleaning Certification Test Questions ?
Myself, and several others are working on test questions for RCIA roof cleaning certifification.
There has been some discussion as to a written vs a verbal test.
I am from the "keep it simple" school of thought.
How do you guys FEEL about a verbal vs a written test ?
I, and several other experienced roof cleaners feel we can tell by talking with someone IF they can clean a roof, or not ?
What do YOU think ?