Output is the end product of a process. For example, the output of the billing correction process is a revised, accurate invoice.
Measuring the volume of output gives you an idea on the throughput. How would you use that data?
Let’s say the billing correction process delivers 50 corrections today. The quantity doesn’t tell you a lot other than 50 corrections are done.
Does it happen to be 50 because that’s all the invoices that require correction? Or is 50 the capacity of the billing clerks, given the time they could allocate to corrections?
Output measurement is not meaningful if you don’t use it in the right context.
For the billing correction example, it would be more meaningful to the number of incorrect invoices with the total number of invoices sent for the month, which gives you a sense of billing accuracy.
Or, compare the time used to correct invoices with the time spent on other tasks, which gives you an appreciation of the significance of the effort spent.
With output measurement, you need to translate it into useful insight for business decisions.