I am applying to PhD programs in educational sciences and they sometimes ask for a writing sample. I am undecided about sending part of my MA thesis or an empirical paper that is in preparation. Each has its own limitations.
MA thesis: It is not recent (I defended it in 2014) and its sections are usually longer than the required page number or word limit. Breaking up these sections to make them fit the requirements doesn't feel right either.
Empirical paper: It is still in preparation and is sometimes shorter than the required length.
I should also mention that I have a first-author publication with two other co-authors, but I keep reading that I should not send it as my writing sample.
So how should I proceed? Do I have to exactly meet the length requirements? Should my writing sample be on a recent topic? Is the published article or the paper in preparation a better choice?