2 Replies Latest reply on Nov 8, 2018 4:42 AM by rhonsberg

    Dixon's q-test in IR

    isaac

      Hello ,

      I'm using openlab chemstation edition software version C 01.07.SR2 and i'd like to create a sequence summary report which report the dixon's Q-test. My sequence have 5 level of calibration with 3 run for level.Q test, is used for identification and rejection of outliers and it's apllied on peak_area.

      Application of the Dixon Q-Test: .1. Arrange the number of values “N” in ascending order. x1 < x2 < . . . < xN

      2. Calculate the experimental Q-value (Qexp). This is a ratio of the difference of the suspect value from the next nearest value divided by the range of the values. For testing x1 or xN (as the only possible outliers) we use the following

      Qexp values: Qexp = ( x2 - x1) / ( xN - x1) or Qexp = (xN - xN-1) / ( xN - x1)

      3. The obtained Qexp value is compared to a critical Q-value (Qcrit) found in the following table. This critical value should correspond to the confidence level (CL) we have decided to apply in the test (at minimum: CL=95%).

      If Qexp > Qcrit, then the suspect value can be characterized as an outlier and it can be rejected, if not, the suspect value must be retained and used in all subsequent calculations.

      For 3 value  Qcrit.(at CL=95%). is 0.970.

      1 I Create a table with group repeat criteria (calibration level) with a descending order sorting option peak_area

      for the formula Qexp = ( x2 - x1) / ( xN - x1) in my case xN is max(peak_area) x1 is min(peak_area) the problem is X2 how i can put this value in a variabile ?

       

      thank's a lot.

        • Re: Dixon's q-test in IR
          ryoboyle

          Hello,

           

          I added tags to this post to increase visibility.

          • Re: Dixon's q-test in IR
            rhonsberg

            Hello. Please see appended example template. It contains a table, which is filtered on a specific compound and sorted by peak_area. I'm using the last() and previous() function to write a value in two additional columns. These two columns contain the smallest and 2nd smallest value of in the peak_area. These are then saved in variables you can use for further calculation.

            If the order of the sorting is reversed you will get the largest and the 2nd largest value.

            To get this into your report, just group all report items and save the composite group. Then open your template and drag the group into the template. You then modify it as needed (and hide the table so that it's not shown in the report).

             

            Hope this is what you were looking for.