Letters of Recommendation - researchers not in the field of stats?

[dmacfour]

My biggest concern with PhD applications is going to be who to use as a recommender. I finished a course based masters in statistics a couple of years ago and could tap some of the faculty for a letter, but to be honest I didn't get to know them well at all. Outside of that, my letters would have to come from researchers in sleep or behavioral science. None of them have a formal background in math or stats (closest is a guy who specialized in psychometrics), so they wouldn't be able to say a lot about my quantitative abilities. Mostly just the way I applied statistics to their particular problems. 

Is this going to be problematic? 

[Nothalfgood]

As a fellow applicant during this stressful application season, I can sympathize with your issue, but I would say that your references probably aren't that problematic. I think that a master's student in your position needs to show good preparation for research moreso than coursework. The fact that you have some good research-related references can only be good for you.

Have you displayed a good math / stats background in your application outside of your letters? If your grades are up to snuff, then the answer is probably Yes! Would it help to have a mathematician write well of you? Of course it would. It's probably not a good idea to include one's letter just for the sake of having it, though. You may not have as strong a profile as you would like to have, but I think the most important thing is that you have someone who knows you professionally and thinks well of you.