Evaluation of PT results


You have collected the data reported in the frame of your PT.
It is time to perform the data evaluation according to ISO 17043 and ISO 13528.

Follow the instructions below.

WARNING: Introduce data/information in the "red" and "grey" cells only.

Introduce data in a protected cell will re-initialise the worksheet (your data will be lost!!).
The same will happen if you reload/refresh the webpage.


The calculation sheet will open in a separate window (click the LINK).



Provide the following information:

  • PT name (optional);
  • measurand (recommended);
  • reporting unit of the measurand (recommended);
  • relative standard deviation for proficiency assessment (SDPA or spt,%)
    Note: the Horwitz relative standard deviation for reproducibility is provided for information;
  • assigned value (xpt);
  • (standard) uncertainty contribution due to characterisation (uchar);
  • relative (standard) uncertainty contribution due to inhomogeneity (uhom(%),in %);

Note: the (standard) uncertainty contribution due to instability, ustab(%), is set to zero (assuming that the material is stable).

  • For each laboratory introduce:

        Limitation: max 30 laboratory;

  • Laboratory codes (01 or L01 or N01 or C01) – introduce in 2nd column
  • reported values (xi);
  • reported (expanded) uncertainty (±);
  • coverage factor (k);
  • Instrumental technique used.


Review the information provided by the sheet

  • Was uchar correctly introduced? Check uchar(%).
  • Check if u(xpt)/spt < 0.3. If yes, z score is applied; if not z’ score is used instead.
  • Was the data properly introduced? Check
    (i) the relative standard uncertainty (RSD);
    (ii) the reported results & associated uncertainties in the graph.
  • For each laboratory result introduced the sheet scores according to D%, z (or z’). In addition, when measurement uncertainties (MU) are provided, zeta scores are calculated and MU are evaluated.
  • IF the uncertainty (±) is not available, u(xi) is set to zero.
  • IF no coverage factor is provided, set k = 1.73 (half-width of a rectangular distribution).
  • IF less than 30 lab values are introduced, filter out the “blank” values in the "LAb code" column.

Finally, you can sort the data by Lab code, by (increasing) reported value, by analytical method or by MU category
and check the resulting graph.


To view the calculation sheet, click the LINK.


For more information, refer to:

  • ISO 17043:2010 - Conformity assessment — General requirements for proficiency testing
  • ISO 13528:2015 - Statistical methods for use in proficiency testing by interlaboratory comparison


The information above is provided "as is" without warranty of any kind, either express or implied, including, but not limited to, fitness for a particular purpose and absence of errors in the application. The entire risk as to the use, quality, and performance of the application is with the user. The owner of these Tools will not be liable for any incidental, consequential, direct or indirect damages including but not limited to the loss of data, loss of profits, or any other financial loss arising from the use or inability to use the application provided.