I'm working on a paper with someone from a different institution. I'm first author.
The data analysis has been done, but there are several ways to interpret the result. I proposed a survey of the population under study as a way to distinguish between mechanisms and his first reaction was that he liked the idea.
I then came up with the survey and have done all the programming. My co-author knows the population involved (as he comes from there), so I'm reliant on his connections.
The problem is, he keeps putting it off, saying "next week, I have commitment X" (where commitment X changes according to week).
I've talked to various peers at my current institution (not involved with my study), and all agree a survey would be a good idea. So it's unlikely that a survey is bad in the first place.
There seems to be a hidden reason for why he keeps delaying the survey release (all he has to do is to ask his contacts to distribute the survey).
How should I approach him? I intend to tell him, basically, that I'm uncomfortable about this situation, that I have difficulty understanding the reasons behind the delay, and that if there are hidden reasons why he appears to be reluctant to roll out the survey, he should let me know. Is this is good idea, and is there anything else I can add?