AS 2891.14.15:2018 – Methods of sampling and testing asphaltMethod 14.15: Mean, standard deviation coefficient of variation and characteristic values.
When any or all of the mean, standard deiation. coefficient of variation and characteristic values of a set of test results are to be determined, they shall be calculated in accordance with this Standard. It shall be permissible to reject abnormal test results before performing the calculation. A result may be assessed as being abnormal only if a specific reason for its abnormality is clearly evident (see Main Roads Western Australia Engineering Road Note X). The reason for its rejection shall bc reported
In practice, specifications may require that test sites for each result be essentially randomly selected in accordance with an appropriate test method such as AS 12g9.l.4.l or
AS 12X9.l,4.2,
The actual statistical values to be calculated will depend on the specification requirements.
Individual results obtained in thc appropriate test shall not be rounded before use in calculations.
As the results to be reported have been subject to statistical analysis, they shall be reported to a greater precision than that indicated in the individual test methods, but to not more than one extra significant figure (for example, for density ratio determined in accordance with ASNZS 2891.14.5 where individual results arc reported to the nearest 0.5%, the statistical values may be reported to the nearest 0,1%).
Calculate the following, as required:
NOTE: The acceptance constant(k) is usually detailed in the specification.However,whcn thisvalue is not specified, the commonly used values are shown in Table Al of Appendix A.Alternatively, the value may be derived from the tables listed in Main Roads Western AustraliaEngineering Road Note 8.
The following shall be reported, as required:
(a) The characteristic values of the test results and the acceptance constant used.
(b)The mean value of the test results.
(c)The standard deviation of the test results.
(d) The number of individual valucs used.
(e)Any individual results excluded from the calculations and the rcason for the rejection.
(f) Reference to this Standard,AS 2891.14.15.
Additional information, as required by the test methods used to determine individual values,shall also be reported.