tolerance-GLO

Tolerance

The Tolerance field defines the Measured Tolerances and Reconciled Tolerances for all measurement devices (meters, tanks, analyzers and transfers) as a number of standard deviations.

For example, if the Tolerance is 2, a meter tolerance given as 6% implies that it has a standard deviation of 3%. A tank with a fixed tolerance of 1000 bbls has a standard deviation of 500 bbls. With a tolerance of two standard deviations, 95% of raw and reconciled values can be expected to fall within two standard deviations of the real value for the meter. But 5% of readings fall outside this range, in the tail regions of the normal curve. These readings appear to be in error when they are actually correct.

If the Tolerance for meters is altered to three standard deviations, which equals a 99% confidence level, only one percent of readings fall in the tail regions of the curve.