**Active Standard: D3180 - 15**

Developed by Subcommittee: D05.21 | Committee D05 | Contact Staff Manager

**1. Rationale**

Data Rounding: Attempts to use data rounded and reported, e.g., to two decimal places, to calculate other data found in the same report may not yield the same numerical results. This apparent error is because all intermediate calculations used to create the reported data are carried out to as many places as the computing device will allow (e.g., 14 decimal places), with rounding occurring only at the time that the final results are published. As the report does not display, e.g., 14 decimal places, use of some, rounded reported values to calculate other reported values will not be as precise or as accurate as using unrounded values, which are available only within the computing system. Cumulative Data Calculation: Analytical data is weight-averaged in order to calculate the vessel composite for a series of vessel sublot samples that have been independently collected, processed, and tested. Similarly, analytical data from individual 10-car sublots may be weight-averaged to obtain a train composite, representing the content of the entire, e.g., 80-car train. Shift-by-shift data may be weight-averaged to obtain the quality of coal in a silo or in a particular ground storage area. Analytical data obtained from a series of sieve fractions or from a series of specific-gravity fractions may be weight-averaged to calculate the analytical data that would have been obtained had the sample been sieved over a specific sieve or had been subjected to a specific-gravity separation at a desired specific gravity. The weight-averaging of such analytical data is performed incorrectly and may lead to wrong decisions based upon such data whenever the analytes to be weight-averaged are on one moisture basis and the mass of the fractions to be weight-averaged are on another moisture basis. This weight-averaging error can be multiplied whenever a series of weight-averaged data is used to develop a cumulative data table, e.g., with sieve or washability data. The farther apart that the moisture contents of the moisture-bases used are, the greater will be the error whenever not using the proper moisture bases. The proposed changes to ASTM D3180 (which is under the jurisdiction of ASTM D05.21) will provide guidance on how these calculations are to be performed.

**Keywords**

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**Date Initiated:**

07-10-2014

**Technical Contact:**

Ronald Graham

**Item:**

015

**Ballot:**

D05 (14-04)

**Status:**

Ballot Item Approved as D3180-2015
and Pending Publication

**Item:**

016

**Ballot:**

D05 (14-04)

**Status:**

Ballot Item Approved as D3180-2015
and Pending Publication

**Item:**

017

**Ballot:**

D05 (14-04)

**Status:**

Ballot Item Approved as D3180-2015
and Pending Publication