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Chemistry LibreTexts

Signals and Noise

  • Page ID
    283112
  • Classroom Exercise: Accuracy and Precision

    Rate the Analysts with respect to accuracy and precision of their measurements.  The x axis is the absolute error of the value they measured minus the true value.  The lines show the means. 

    Measurements_Analyst1-4.png

    Data from: C. O. Willits and C. L. Ogg, J. Assoc. Offic. Anal. Chem., 1949, 32, 561. (adapted from Skoog, Analytical Chemistry, 2015).

     

    Analyst 1:

     

     

    Analyst 2:

     

     

    Analyst 3:

     

     

    Analyst 4: 

     

     

    Note that Analysts 1 and 2 did the same analysis but did not get the same results.  If you were running a lab, what suggestions might you make for this analysis to try to get the two analysts to be standardized?  

     

     

     

     

    What sources of error might lead to the problems of Analyst 2?

     

     

     

    Note that Analysts 3 and 4 did the same analysis (but not the same one as Analysts 1 and 2).  If you were running a lab, what do you think about this assay and what suggestions do have to make this analysis both accurate and precise?   

     

     

     

     

    What sources of error might lead to the problems of Analyst 3?

     

     

     

     

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