"Bias Study is the difference between the true value (reference value) and the observed average of the measurements on the same characteristic on the same part."

Bias Test is sometimes called Accuracy Test. Accuracy (and bias) refers to the absolute correctness of the measurement system relative to a standard. There are many standards. For example, one method of checking the accuracy of a laboratory weigh scale is to put a standard 10 gram weight on the scale. On average, the scale should read 10 grams if it is accurate.

Bias represents a measure of the systematic error of a measurement system. Here are some reasons for excessive bias including:

  • Instrument needs recalibrating
  • Worn equipment
  • Damaged master
  • Improper calibration
  • Temperature
  • Humidity
  • Cleanliness