Random Error

Random error is the irreproducibility in making replicate measurements and affects the precision of a result. The distribution of random errors follows a Gaussian-shape "bell" curve. The precision is described by statistical methods such as a standard deviation or confidence limit.

Systematic Error

Systematic errors are errors that produce a result that differs from the true value by a fixed amount. These errors result from biases introduced by instrumental method, or human factors.

An example of an instrumental bias is an incorrectly calibrated pH meter that shows pH values 0.5 units lower than the true value. An example of a method error would be partial loss of a volatile analyte during the ashing step in graphite furnace atomic absorption (AA) spectroscopy. An example of human bias is a student who records titration endpoints beyond the true endpoint due to color blindness.

Systematic errors can be identified and corrected by analyzing standards that closely match the real sample.

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Further Information

/chem-ed/data/error.htm, updated 10/14/96

Copyright © 1996 by Brian M. Tissue, all rights reserved.

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