1.1 There is uncertainty when reviewing test results from another laboratory or even two tests from the same laboratory and the results differ. The purpose of this practice to determine whether these differences are statistically different and meet a test of reasonableness. Reasonableness being defined as test results that are within the precision and bias parameters for the test being performed. Test results with a practical significant difference would be those with differences in results that exceed the precision and bias limits for the test procedure. This check for reasonableness is important when small samples sizes, 20, are being compared to eliminate false positives. Thus, this practice can be used to determine whether the differences are statistically different, but not fail the test of practical significance ly differentThis practice may also be used to determine whether changes in test procedures, such as sample conditioning, creates a statistically different measured response during testing. Further, this practice checks for reasonableness, that is whether the changes create variability that is less or greater than the precision and bias estimates for the test procedure. This practice maybe used to determine test results are reasonable and further, be used as a guide to determine whether changes in testing procedures reduce testing variation. This practice makes use of the paired-t test and measured precision and bias to determine statistical differences between data populations. 1.2 Units--The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
This practice will be used by researchers, government agencies, and in quality control testing to determine the reasonableness of test result differences and to determine the effect of changes in test procedures such as sample conditioning.
Keywordsstatistical differences, reasonableness, conditioning; paired t-test; practical significance, precision and bias
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
Draft Under Development