Section 1: Percentage Error

Any measurements you make will have some error in them because measuring equipment is not 100 % accurate. You need to be able to calculate the error as a percentage of the the total measurement - you need to be able to calculate the PERCENTAGE ERROR.


"A pharmacist weighs 400 milligrams of a substance on a balance with a sensitivity of 10 milligrams. What is the maximum potential error expressed as a percentage?

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The percentage error is the PROPORTION that the error is of the total measurement, expressed as a per cent. This leads to the equation:
Percentage Error =               Error               x 100 %
Actual Measurement
The SENSITIVITY of the balance gives you the ERROR in milligrams.
Thus the error is 10 milligrams. Thus:
Percentage Error =    10    x 100 %
400
Percentage Error = 2.5 %