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Posted by Lewis on April 04, 2005

In Reply to: RULE OF THUMB posted by Fred on April 04, 2005

: : Does anyone know the word which means an equation which isn't scientifically proven but is known through knowledge? i.e like rule of thumb.
: : Thanks for your help

: Are you talking about what is known a priori (vs. a posteriori)?

isn't 'rule of thumb' a rather poor example? from what I have heard the rule of thumb comes from the old legal principle that it was acceptable to beat your wife with a stick providing that it did not have a diameter larger that your thumb. a 'rule of thumb' is thus a simple principle (usually relating to measurement) easily understood and applied.

'rough approximation' is the expression I would use for a quick calculation that has a fairly well-known application - eg. "pi" being 22/7 might fit that although the mnemonic of the letter numbers in "how I wish I could calculate pi" is pretty handy for 3.141592.

'rules of thumb' arise in particular industries and I can't think of any examples from the real world, but if somebody says - "oh, it's 3 times the height in bags of gympsum and add 20%" you may have spotted one.