Worldwide Open Proficiency Test: Determination of ... - Nucleus - IAEA

4.1. General
Draft, page 18
4. RESULTS AND DISCUSSION
In this PT, 6505 measurement results were reported to the IAEA from 266 laboratories in 69
countries.
One month after the deadline for reporting results, each participant obtained an individual
evaluation report using a dedicated on-line application to give a rapid feed back on the
performance of the laboratories.
The participants’ data along with the statistical performance evaluation were compiled and
sorted by analyte and reported in Appendix I.
The number of reported results and obtained evaluation as acceptable/warning/not acceptable
of each laboratory is presented graphically in Figure 10. This way of presenting results
evaluation allows the participating laboratories to compare their results to those reported by
other laboratories and to benchmark their performance level with peers. In addition, all
participating laboratories could share the technical information provided in the Appendix I to
identify the commonly applied analytical procedures, the listed information could also be used
to find out the weak or strong points in the analytical procedure adopted by each laboratory
when comparing the laboratory evaluation results with other participating laboratories.
To have an overview of the participants’ performance for each specific radionuclide, each
radionuclide was studied individually. Table 4 shows the distribution of results scored as
acceptable/warning/not acceptable for each evaluated radionuclide and for each sample.
The S-shape charts of the reported analytical results are presented in Appendix I to give an
overall view of the analytical performance of the laboratories population in this PT. The list of
participating laboratories is presented in Appendix II.
The overall evaluation showed that 26% of all reported results failed to meet the PT criteria.
Contrary to expectation, it was noticed that the percentage of acceptable results for
radionuclides in moss-soil was slightly higher (around 10%) than the observed performance
level for the water samples. This could be attributed to the relatively low level of radioactivity
in water samples.
To compare the performance level of each laboratory a normalized average analytical
performance and the percentage of “Not Acceptable” scores were calculated in the following
way:
Where:
Normalized average performance (%) = ((A+W)/ NRR)*100
Percentage of “Not Acceptable scores” (%) = (N/NRR)*100
A: number of obtained “Acceptable” scores
W: number of obtained “Warning” scores
N: number of obtained “Not Acceptable” scores
NRR: Total number of reported results.
The results of the calculation are shown in Table 5 in ascending order according to the
normalized average performance value.
This approach of presenting the level of performance of all laboratories allows each
participant to compare its own performance level with the level of peers.