Regarding the idea that to forgive is Divine, we too should be forgiving. Because human error is not avoidable, it should not be considered blameful. Fagan  emphasized that blaming makes people defensive and harms error detection and correction. The correct attitude is that error is inevitable and that only a stance that rejects blamefulness is likely to be effective.
One page at this website is a minipaper on general human error theory. We would urge readers to study Baars  and Reason  for more detail on the inevitability of human error.
This website contains a number of tables organized in the following way:
Errors in Multi-Step Tasks. Many tasks involve a series of smaller actions. A good example of this is commands typed at a command line. When there are many small tasks, error rates multiply. In addition, as the number of steps grows, the possibility of short term memory overload increases.
Spreadsheet Errors. This page links you to the Spreadsheet Research (SSR) website which contains such data.
For programming, we have especially rich error data thanks both to experiments and to code inspection studies that have reported the error rates they found. In programming, errors are called faults, and they are measured in terms of faults per thousand lines of (non-comment) source code, faults/KLOC. We have converted these figures into percentages for easier comparison with other data at the website.
Normal Development: This table shows error rates for normal traditional development. Data from thousands of code inspections are included.
Formal Development: New formal method try to prevent errors from happening in the first place. Their error rates are comparable to those in normal traditional development, after code inspection.
Late Inspection: This table shows error rates after individual modules have been tested and then combined into a full system. This table shows error rates found just as the system is about to go out the door.
Test-Retest: One study had students do procedures twice and studied
how errors and correct performance on the first part were related to errors
and correct performance in the second.
General Error Detection. This table looks at error detection in other
Bibliography. Here is where to find all those citations listed in [square