Accuracy and Bias

The accuracy of a sample reflects how closely the sample mean (the character x with a bar over it) represents the true population mean (greek character mu). Sample accuracy is jeopardized by systematic factors associated with the placement or measurement of sample units, that lead to cumulative errors or biases in the sample mean. These may be caused by inherent flaws in our sampling procedures, or by personal prejudices during data collection.

Sample accuracy cannot be assessed or corrected after the data is collected, because the true population mean remains unknown (if it were known, we wouldn't be sampling!). The best way to ensure accurate data is to incorporate safeguards into the sampling process that protect against bias. These safeguards include:

References and Further Reading

Bonham, C.D. 1989. Measurements for terrestrial vegetation. John Wiley Son, New York, NY. pp 10-11.

Cook, C.W., and J. Stubbendieck. (eds). 1986. Range research: Basic problems and techniques. Society for Range Management, Denver, CO. pp 215-220.