Terminologies Discussed in ASTM E177
A total of 27 terminologies are discussed in the standard. The terminologies and definitions as per ASTM E177 are provided in the following table:
| Terminologies | Definitions as per ASTM E177 | |
| accepted reference value | “a value that serves as an agreed-upon reference for comparison, and which is derived as (1) a theoretical or established value, based on scientific principles, (2) an assigned or certified value, based on experimental work of some national or international organization, or (3) a consensus or certified value, based on collaborative experimental work under the auspices of a scientific or engineering group” | |
| accuracy | “the closeness of agreement between a test result and an accepted reference value” | |
| bias | “The difference between the expectation of the test results and an accepted reference value.” | |
| characteristic | “a property of items in a sample or population which, when measured, counted or otherwise observed, helps to distinguish between the items” | |
| coefficient of variation | “for a nonnegative characteristic, the ratio of the standard deviation to the mean for a population or sample” | |
| intermediate precision | “precision of test results from tests conducted on identical material by the same test method in a single laboratory at the same or various times with one or more known sources of variability controlled at multiple levels” | |
| intermediate precision conditions | “conditions under which test results are obtained with the same test method using test units or test specimens taken at random from a single quantity of material that is as nearly homogeneous as possible, and with changing conditions such as operator, measuring equipment, location within the laboratory, and time” | |
| laboratory precision | “The precision of test results obtained within a laboratory for identical material under conditions that include all known sources of variation within the laboratory over extended periods, often months.” | |
| observation | “the process of obtaining information regarding the presence or absence of an attribute of a test specimen, or of making a reading on a characteristic or dimension of a test specimen.” | |
| observed value | “the value obtained by making an observation” | |
| precision | “the closeness of agreement between independent test results obtained under stipulated conditions” | |
| repeatability | “precision of test results from tests conducted within the shortest practical time on identical material by the same test method in a single laboratory with all known sources of variability controlled at the same levels” | |
| repeatability conditions | “conditions where independent test results are obtained with the same method on identical test items in the same laboratory by the same operator using the same equipment within short intervals of time” | |
| repeatability limit | “the value below which the absolute difference between two individual test results obtained under repeatability conditions may be expected to occur with a probability of approximately 0.95 (95 %)” | |
| repeatability standard deviation | “the standard deviation of test results obtained under repeatability conditions” | |
| reproducibility | “precision of test results from tests conducted on identical material by the same test method in different laboratories” | |
| reproducibility conditions | “conditions where test results are obtained with the same method on identical test items in different laboratories with different operators using different equipment.” | |
| reproducibility limit | “the value below which the absolute difference between two test results obtained under reproducibility conditions may be expected to occur with a probability of approximately 0.95 (95%).” | |
| reproducibility standard deviation | “The standard deviation of test results obtained under reproducibility conditions” | |
| standard deviation | “The square root of the average or expected value of the squared deviation of a variable from its mean; —of a sample, s, the square root of the sum of the squared deviations of the observed values in the sample divided by the sample size minus 1.” | |
| test determination | “The value of a characteristic or dimension of a single test specimen derived from one or more observed values” | |
| test method | “A definitive procedure that produces a test result” | |
| test result | “The value of a characteristic obtained by carrying out a specified test method.” | |
| test specimen | “the portion of a test unit needed to obtain a single test determination” | |
| test unit | “The total quantity of material (containing one or more test specimens) needed to obtain a test result as specified in the test method.” | |
| trueness | “The closeness of agreement between the population mean of the measurements or test results and the accepted reference value.” | |
| variance | “Square of the standard deviation of the population or sample” |
Tests Related to ASTM E177
ASTM E177 is similar to ASTM E691, which offers guidelines for conducting inter-laboratory experiments to estimate the precision of a test method.
