Error Analysis?

[Rafferty]

I'm studying Speech and Language Therapy and was wondering if anyone could explain to me what Error Analysis is exactly? I've been asked to discuss the importance of error analysis in Aphasia with reference to PALPA and BDAE. Just not 100% sure what error analysis is and cant find a clear definition in any books/online/lecture notes.

Thanks a lot

[markja]

you've just made my head hurt.!!!!!