Estimation of measurement uncertainty in chemical analysis

Self-test 10.2

Here you can test your understanding how the uncertainty component accounting for the random effects can be estimated in practice.

1. A laboratory wants to estimate the within-lab reproducibility component (component accounting for the random effects) of measurement uncertainty of protein content determination in different foods. For this protein content in a control sample of smoked sausage was determined repeatedly during a time period of almost one year. Every day when this smoked sausage was analysed only one parallel measurement was made. The following results were obtained:
WeekResult (g/100g)
318.1
520.5
1118.3
1419.1
1519.3
2720.2
3419.7
4119.5
4218.6
4820.1
 

Please calculate the within-lab reproducibility component of uncertainty (please give 2 or 3 decimals). Absolute uncertainties can be used in this case.

The reproducibility component is found as the standard deviation of the results obtained on different days.

2. Which of the following is true?

3. Which of the following issues are important in determining sRW?


 

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