Monday, January 30, 2006


The spreadsheet model I built over the weekend was knocked into a cocked hat by a colleague who walked into the office on Monday and said something was wrong with the numbers. I spotted the problem immediately. I had inadvertently used a monthly factor for total hours worked that was 600% too high. When I corrected for that, all other hourly entries were suddenly wrong. It didn't make any difference that everything was crossfooted and correct internally.

Garbage in: Garbage out. It took three attempts to get the numbers back into the correct proportions.

What's the lesson here? Ah yes, crossfooting wrong numbers makes for internally consistent error. Good to know.


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