Tolerance
Tolerence in measurement is the amount of variation that is permitted within a measurement. There is a certain amount of variation in measurement systems, devices, and readouts that will not have a significant impact on the outcome. However, any amount of variance that goes beyond the tolerance will result in inaccuracy. Some specific dimensions that have a tolerance include the physical context in which the measurement takes place (ex. temperature), the physical nature of the object being measured, or the physical properties of the system doing the measurement. The most important factor to determine is what amount of tolerance is acceptable without having a negative outcome. Tolerance will change between different measurement systems, as well as between varying fields utilizing measurement. The tolerance required in construction will be slightly different from that required in engineering. Within a normal distribution there are inherence variances among input and output. Knowing the tolerance of a measurement tool will help you to account for all of the variance statistically.