I've already made this comment elsewhere on this thread, but just for completeness sake...
The problem with reading off a 30x variation (or even >10x) from Norvig's results is that it discounts the possibility that the same person might take different amounts of time for tasks (relative to the others in the group).
For instance, you might have people in the group that have already worked some variation of that problem. Or you might have some that had colds, were distracted, or just do badly on that sort of enumeration problem, but are killer at other problems. Every one of these possible discrepancies cuts away at the expected magnitude of the actual overall productivity difference between programmers, and should be accounted for.
Of course, since that difference is not what was being studied, they didn't set up the experiments to gather the data we'd need to best estimate the real productivity differences, so it's hard to say what we should conclude...I'm sure there are people that are 1/30th as productive as the best programmers, but what we'd really want to know is how typical they are, and what the overall distribution looks like. That's far less clear.
The problem with reading off a 30x variation (or even >10x) from Norvig's results is that it discounts the possibility that the same person might take different amounts of time for tasks (relative to the others in the group).
For instance, you might have people in the group that have already worked some variation of that problem. Or you might have some that had colds, were distracted, or just do badly on that sort of enumeration problem, but are killer at other problems. Every one of these possible discrepancies cuts away at the expected magnitude of the actual overall productivity difference between programmers, and should be accounted for.
Of course, since that difference is not what was being studied, they didn't set up the experiments to gather the data we'd need to best estimate the real productivity differences, so it's hard to say what we should conclude...I'm sure there are people that are 1/30th as productive as the best programmers, but what we'd really want to know is how typical they are, and what the overall distribution looks like. That's far less clear.