for Bias Studies If the bias is statistically non-zero, look for these possible causes:
Error in master or reference value. Check mastering procedure.
Worn instrument. This can show up in the stability analysis and will suggest the maintenance or refurbishment schedule.
Instrument made to wrong dimension.
Instrument measuring the wrong characteristic.
Instrument not calibrated properly. Review calibration procedure.
Instrument used improperly by appraiser. Review measurement instructions.
Instrument correction algorithm incorrect.
If the measurement system has non-zero bias, where possible it should be recalibrated to achieve zero bias through the modification of the hardware, software or both. If the bias cannot be adjusted to zero, it still can be used through a change in procedure (e.g., adjusting each reading by the bias).
Since this has a high risk of appraiser error, it should be used only with the concurrence of the customer.
source of Bias Studies: Analysis of measurement systems
