If you have access to GP Power Tools or Rockton Toolbox, you can use their security profiler to help with this. I think they both have free trials available.
(I don't have HR loaded so I am not able to look it up. Depending on which version you are on - and whether it is before/after HR was returned to the developer - the security setup may be different.)
David Musgrave, developer of GP Power Tools, has documented a SQL (technical) method for determining the security information:
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