Conducting proficiency tests with large numbers of participants are not a problem because the ISO standard 13528:2015 describes many indicators that allow for proper assessment. However, there are proficiency testing (PT) schemes that involve only few participants. In such situations, the same difficulties exist for the selection of proper indicators and the criteria for assessing the participants' achievements. The Institute for Chemical Processing of Coal in Zabrze, Poland organised a round of PT of the determination of gypsum parameters. The results from six participants from Polish research entities and independent laboratories and methodology for the organisation this PT are presented. The performance evaluation criteria were determined using participants results due to the inability to use the metrologically valid procedure. The performance of the participants was evaluated using z′ and zeta scores.

中文翻译：

---

用少量参与者进行石膏参数测量的实验室间能力测试

对大量参与者进行能力测试不是问题，因为 ISO 标准 13528:2015 描述了许多允许进行适当评估的指标。但是，有一些仅涉及少数参与者的能力验证 (PT) 计划。在这种情况下，选择合适的指标和评估参与者成绩的标准也存在同样的困难。位于波兰扎布热的煤炭化学加工研究所组织了一轮关于石膏参数测定的 PT。展示了来自波兰研究实体和独立实验室的六名参与者的结果以及该 PT 组织的方法。由于无法使用计量有效的程序，因此使用参与者的结果来确定性能评估标准。