Set up the internal quality control by choosing suitable control samples and set-up control charts with preliminary control limits (preferably target control limits) - see Nordtest TR 569 "Trollbok" version 2018 for further guidance, www.nordtest.info

 

 Document available in more than 15 languges   

Document available in more than 15 languges

 

Version 5 2018 has the following news

  • more focus on target control limits. In cases where the client’s demand is lower than the performance of the method, wider control limits can be set. Since this will results in fewer out of control values we recommend laboratories consider this option – see example 1,2,5 and 7;

  • long-term evaluation (chapter 10) now discusses changing of control limits and central line in separate paragraphs;

  • pooled standard deviation
    * combined standard deviation is now more correctly called pooled

    standard deviation;
    * pooled standard deviation is recommended to obtain the standard deviation for range charts;
    * an example of pooling standard deviation for sr and sRw from an internal control measuring three replicates in every analytical run, example 10, is added. If all results were used to calculate sRw too low estimate is obtained resulting in too narrow control limits;

  • for range chart the best samples to be used are test samples selected among the samples to be analysed in that analytical run – examples have been updated.