AS 2891.14.15 pdf download – Methods of sampling and testing asphaltMethod 14.15: Mean, standard deviation coefficient of variation and characteristic values
This Standard sets out the method for calculating the mean, the unbiased standard deviation,coefficient of variation and characteristic values of a set of test results.
These values are most commonly specified for density ratio and per cent air voidsdetermined in accordance with AS/NZS 2891.14.5 but may also be applied to other testresults for asphalt, other construction materials and processes.
The following documents are referred to in this Standard:AS
Methods of testing soils for engineering purposes
12188.8.131.52 Method 1.4.1: Sampling and preparation of soils—Selection of sampling or
test sites——Random number method
12184.108.40.206 Method 1.4.2: Sampling and preparation of soils—Selection of sampling or
test sites——Stratified random number method
Methods of sampling and testing asphalt
Method 14.5: Field density tests—Density ratio and percent air voids of
Main Roads Western Australia Engineering Road Note 8,Statistically based quality controlfor density in road construction.
When any or all of the mean, standard deviation, coefficient of variation and characteristicvalues of a set of test results are to be determined, they shall be calculated in accordancewith this Standard. It shall be permissible to reject abnormal test results before performingthe calculation.A result may be assessed as being abnormal only if a specific reason for itsabnormality is clearly evident (see Main Roads Western Australia Engineering RoadNote 8).The reason for its rejection shall be reported.
In practice, specifications may require that test sites for each result be essentially randomlyselected in accordance with an appropriate test method such as AS 12220.127.116.11 orAS 1218.104.22.168.
The actual statistical values to be calculated will depend on the specification requirements.Individual results obtained in the appropriate test shall not be rounded before use incalculations.
As the results to be reported have been subject to statistical analysis,they shall be reportedto a greater precision than that indicated in the individual test methods, but to not more thanone extra significant figure (for example,for density ratio determined in accordance withAS/NZS 2891.14.5 where individual results are reported to the nearest 0.5%, the statisticalvalues may be reported to the nearest 0.1%).
Calculate the following, as required:
(a)The mean of the individual test results (? ) from the following equation: