Balancing Contribution to Data Set from Sources

I haven't touch stats in a while, and needs a hint on the mathematical term on what it is that I am actually doing so I can further research on how to actually do it.

Consider a set of data built from results of a chemical test. The aim of the test is for the result to reach a certain target range. Say the test was performed on subject A for 25 times, subject B for 75 times, and subject C for 50 times.

What I need to compute is the percentage of results that is on the target range.

However, I also need to even out the 'contribution' of each subject so that the 'contribution' of each subject would have an equal 'weight' to the percentage of results on target, i.e. results from subject A needs to be twice as strong, and results from subject B needs to be 0.66 as strong.

Of course it's just a matter of scaling the results from each of the subjects, but what is this scaling known as??

Please let me know the proper mathematical term of what this is that I'm doing and the relevant mathematical terms so I can google more out, thanks.