ABSTRACT
Properly, one should acknowledge measurement uncertainty and report the calculated value in a manner that appropriately reflects the precision of the calculated value. There is uncontrolled variation in the processing, testing, source materials, environmental conditions, test machines, operator techniques, sensor discrimination, etc., and these lead to variation in the supposed-to-be exactly-the-same outcomes. To experimentally estimate uncertainty, only use replicate trials, independent trials that should provide the exact same result, because they nominally were run at exactly the same conditions. There are two key measures of deviation from the average: error and standard deviation of the variable. There is a range of values that might be expected when something is replicated. This chapter uses the term uncertainty; however, both the terms “error” and “propagation of error” remain as commonly used labels.
