This probability distribution is usually applied to the resolution limit of the measurement instrumentation (i.e. the displayed resolution or the resolution of internal analogue/digital converters).However, this is not the only source of uncertainty of measurement equipment. There may be uncertainty arising from the measurement algorithm used and/or from the calibration process.If the equipment measures relative values, then there will also be uncertainty in the determination of its datum.A.6.4 Normal probability distributionThe normal probability distribution is represented in Figure A.4.