Ideas to narrow down a master thesis topic within management scope I am choosing (by myself) a topic to research and write about for my master thesis. My criteria are simple: 


I should have enough possibility to research the topic within a company where I work, or company where access to data is available.
The topic should be interesting to me.


Based on both, I have narrowed down the topic of managerial span of control and possibly related topics in corporate management, e.g. unity of control, matrixed organizations, etc.

I am having a difficulty, however, to go further and design the specific question(s) to explore, or hypothesis to build and test. I asking for your help here.

While I can have a fairly good data about the span of control within a given company (or several companies) that I can research, I will for certain have difficulty to obtain other HR related data...
I would suggest that you find a paper published within a good journal in your field and use it as a template. The paper should be (i) on a topic of interest to you, (ii) easy to understand (relative to the norm), and, (iii) using methods that you and your supervisor are familiar with, or can easily learn and use in your own research. To use this paper as a template, simply ensure that you are guided by the structures and logic of the paper in how you present your own. For example, if the paper is about how X causes Y explained through theory Z, you can simply reused some of the argument, while changing one of the variables.