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Hi Mohamed Soltan,
To answer your question, firstly ISO 17025 requirements does not specify that you need to use specific method of calculation. Hence, it up to the organisation to adopt a method to estimate your measurement uncertainty.
There few approach in estimating measurement uncertainty, top down approach and bottoms up approach are some of the approach. If you are chemical testing lab, you may refer to eurachem guide to measurement uncertainty. Them link is as below:
https://www.eurachem.org/index.php/publications/guides/quam
Thank you.
As there is no written guideline in ISO 17025 :2005 on calculation of MOU , however eurachem guideline can be followed for calculation of MOU .
During calculation of MOU to critical factors are random error and systematic errors .
During calculation of MOU to critical factors are random error and systematic errors.
Moreover, the effect of environment also to be considered for MOU calculation.
Standard deviation is calculated using data for a peroid of time ( 6 months to one year ) and is multiplied by 2 to give expanded uncertainity of measurement ; this gives 95% confidence limit.
To calculate the uncertainty in accordance with ISO 17025 it there's the least square method or Monte Carlo. you can also see the GUM and FD X 07-020, FD X 07-028 ....
To calculate the uncertainty we must also know estimate the random and systematic errors for each physical phenomenon by applying 5M.
