HOW ARE THE RESULTS ANALYSED?
For testing programs the evaluation of a laboratory’s performance is normally based on a comparison to consensus values calculated from the results submitted. Proficiency Testing Tunisia PTTn uses a suite of statistical procedures typically based on the internationally accepted method of calculating z-scores. Variation of results both within a laboratory and between laboratories may also be assessed. For calibration programs, laboratory’s results are compared to the values established by a reference laboratory, taking into account the measurement uncertainties assigned to the reference value and those assigned by each participating laboratory. Performance of each measurement is judged by the calculation of the En ratio. Proficiency Testing Tunisia PTTn provides both a final report and a summary sheet at the completion of the program. The final report contains the results
reported by the participants, outcomes of the statistical analyses, graphical presentations of the data and comments on overall performance.
Any queries or disagreements regarding results should be reported directly to the Program Coordinator for the program in question. The Program Coordinator, in conjunction with the Technical Adviser (where necessary) will perform a full review of the results queried by the participant. This review will be conducted in-line with PTTn Corrective Action procedures. PTTn will advise the participant of the outcome of the review. If the outcome of the review is in favour of the participant, then the summary sheet will be amended to reflect the revised evaluation and forwarded to the participant.