SamplingProfiler  run results can be saved to .spr files (Sampling Profiler Results) and later reused for comparison purposes, or for merging, one of the less obvious features of the profiler.
You can merge results by right-clicking on a results tab and selecting… “Merge results”, oddly enough. After this, the samples will be aggregated across the runs you selected, hopefully providing more statistical accuracy .
This can be particularly useful when analysing the results from multiple runs, collected from multiple users in the field via SamplingProfiler’s silent mode for instance. It can also be useful if you collect profiling information from automated test tools, each stressing the same library or base code in different ways.
Merging results isn’t as much about getting high numerical precision on your bottlenecks. Sure, you can use it for numerical accuracy, but who cares if a routine takes 95% or 92.24638% of the CPU time? identifying the bottleneck is usually all that matters.
Merging is about figuring out the bottlenecks that matter in everyday use, bottlenecks which may not come up in your routine tests, or may not be seen as critical when seen in isolation. It can be about getting information on that odd, hard-to-reproduce, slowdown your users may be experiencing from time to time. It can also be about identifying the minor bottlenecks that could be the cause of a “sluggish” feel to your UI.
A last word on the SPR files: those are persistence streams of SamplingProfiler native format, they’re binary, highly compact, and for you, the user, highly proprietary and blackboxy. If you want to do your own analysis on the profiling results, there is an alternative: you can save results as an XML  file, which will include all the data in a verbose fashion. Be warned however that a deceptively small SPR can result in a huge XML file.