[AccessD] bust out the math books

Stuart McLachlan stuart at lexacorp.com.pg
Wed Jan 25 10:52:17 CST 2006


On 25 Jan 2006 at 7:24, Jim Lawrence wrote:

 
> When tax totals are generated then all the tax subtotals are just added
> together. In theory, all the subtotals could be added and the total tax
> could be calculated but the answer would be wrong. This is the same problem
> experience when trying to calculate the average by item and then expecting
> the average for the whole group to add up. It never will.
> 

No, the two are completely separate problems.

Tax totalling problems are caused by rounding errors inherent in the 
process of working with currency which has a minimum sized unit (a cent or 
whatever).  Averaging problems are caused by false assumptions about the 
underlying maths by the  person writing the code.



-- 
Stuart





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