Available to Members only.
The SMRI Inter-laboratory Proficiency Testing scheme
Proficiency testing is an ideal mechanism to give mill laboratory staff the ability to both monitor and improve their analytical capabilities and comprises an interlaboratory system for the regular testing of the accuracy that the participant laboratories can achieve. The primary purpose of proficiency testing is to help laboratories detect and cure any unacceptably large inaccuracies in their reported results and is therefore designed as a self-help system to alert the participants whether they need to improve their analytical practice. These discrepancies could result from malfunctioning or poorly calibrated equipment, possible poor analyst performance or reagent deterioration. The SMRI Interlaboratory Proficiency Testing scheme uses identical VHP sugar samples analysed by the SMRI and factory laboratories at near-monthly frequencies. The results are compared using a statistically derived z-score and displayed graphically. The power of the proficiency scheme lies in the continuous monitoring of the z-score for any particular analysis. The laboratory can record and interpret the accumulative z-scores for a particular analysis in the form of a Shewhart control chart (shown here for raw sugar pol).
The z-score is interpreted as follows:
Twenty laboratories are currently participating in the scheme. The Table below shows the improvement in the number of laboratories achieving Rescaled Sum of Squares values (RSZ – a measure of the z-scores across a season) of less than 10. This indicates there has been an improvement in attention to detail and in the quality of the analyses recorded in the factory laboratories since the introduction of the scheme in the 2015/16 season. All member mills are encouraged to participate in the Scheme.
You must be a registered user and have a valid email address with a participating Member Organisation to access reports of the results, for which
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Send us an email for any queries relating to the SMRI Proficiency Scheme.
Detailed description of the scheme and methodology
Walford SN and Pillay V (2016). The SMRI interlaboratory proficiency scheme – repeatability, reproducibility and more. Proc S Afr Sug Technol Ass 89:457-466. https://sasta.co.za/download/6/2010-2019/510/2016_walford-sn-and-pillay-v_the-smri-interlaboratory-proficiency.pdf
Walford SN and Pillay (2014). The z-score as an alternative measure for the SMRI inter-laboratory testing programme. Proc S Afr Sug Technol Ass 87:118.
https://sasta.co.za/download/6/2010-2019/346/2014_walford-sn_the-z-score-as-an-alternative.pdf. Poster available on request.