AASHTO PP 112:2021 Standard Practice for Recognizing Surrogate Test Methods.
1.1. This practice describes a method to assess the capability of a surrogate test to be used as a substitute for a standard test. The surrogate tests must demonstrate the capability to provide test results similar to the standard test method with a minimum of additional variability. The test results from the standard and the surrogate are compared and the error in their relationship is quanti lied.
1.2. It may he desirable to use a surrogate test to monitor material quality during construction or production. especially if the standard test method uses complcxlexpcnsivc equipment, requires time-consuming sample preparation and testing techniques, uses hazardous materials, or involves destroying a portion of the material. This standard practice is intended to be applied for construction quality control but may also be used for acceptance if specifically approved by the Agency.
1.3. The procedure in this standard should be followed in the evaluation of potential surrogate test methods and to set parameters for their use.
4. PROCEDURE TO COMPARE STANDARD AND SURROGATE TESTS
4.1. The procedure involves three parts. 1) comparing the testing repeatability and reproducibility of the standard test to the repeatability and reproducibility of the surrogate test, 2) identifying the equivalence limit (E) for the test, and 3) measuring the equivalence (upper confidence limit (EUCL) and lower confidence limit (ELCL)) in the means and variance relationship between the standard and surrogate test. Every test method has inherent variability. In using a surrogate test method, the variability of the surrogate test method adds an additional component of variability to the standard test results. If that variability is minimal compared to the benefits of the surrogate test, the surrogate test is acceptable for use. This procedure identifies and quantifies the added variability, establishes a recommended limit to that variability and performs a hypothesis test to test if the difference between the standard and surrogate test results exceeds the identified limit.
4.2. Step 1—Compare the testing repeatability and reproducibility of the standard test to the repeatability and reproducibility of the surrogate test. Step I provides confidence that the surrogate test can be performed with similar variability by comparing the repeatability and reproducibility or by comparing the standard and surrogate test methods using a statistical F-test on the variances. R 9 Appendix X2 describes the F-test procedure, it is also a standard statistical method found in standard computer spreadsheet and statistical analysis programs.AASHTO PP 112 pdf download.