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FAQ

Why do I need sensitivity analysis?

A mathematical model is defined by a series of equations, input factors, para

meters, and variables aimed to characterise the process being investigated. Input is subject to many sources of uncertainty including errors of measurement, absence of information and poor or partial understanding of the driving forces and mechanisms. This imposes a limit on our confidence in the response or output of the model. Further, models may have to cope with the natural intrinsic variability of the system, such as the occurrence of stochastic events. Good modelling practice requires that the modeller provides an evaluation of the confidence in the model, possibly assessing the uncertainties associated with the modelling process and with the outcome of the model itself. Uncertainty and sensitivity analysis offer valid tools for characterising the uncertainty associated with a model.

More information: Sensitivity analysis

Why do certified values and uncertainties of replacement batches differ from the first released batch of a CRM?

Replacement batches are usually produced from different raw materials than th

e first batch of a CRM. Therefore, they do not have the same property values (analyte content etc.). Although we try to match the first batch, this is sometimes impossible or even not desirable: changes in the analyte content routinely encountered in the laboratory should be reflected by changes in the concentration levels of the CRM.

Who owns the trademark?

The European Community owns the ERM® trademark.

The Community licences the trademark to the ERM® partner organisations to mark products accepted as ERM® in accordance with the ERM® rules.

Who owns the ERM® materials?

Each ERM material is owned by one of the members of the ERM® concept.

The owner is fully responsible for its materials, i.e. for production, replacement, stability, storage, product liability etc.

Which value do I use for calibration?

The value mentioned on the certificate is the certified value for the referen

ce material and consequently the value to be used for calibration. But the uncertainty of the certified value has also to be included for the estimation of the measurement uncertainty.

Which method do I have to use?

Any method that is traceable to the same reference as the certified value can

be used.

Which is the best method to perform SA on my model?

The choice of which SA method to adopt is difficult as each technique has str

engths and weaknesses. Such a choice depends on the problem the investigator is trying to address, on the characteristics of the model under study, and also on the computational cost that the investigator can afford.

More information: Sensitivity analysis

Which DNA extraction method should I use?

Reliable results can only be guaranteed if an extraction method validated in

a collaborative trial is used. Some extraction methods and their validation reports are accessible on the web site of the EURL for GM food and feed under the section "Status of dossiers".

Where can I get additional information on my material?

IRMM publishes for each material an extensive report available on this web si

te. This report gives valuable information on methods used by the participants and potential problems besides giving more detailed information on the production of the material.

Where can I find reference materials?

Main sources to locate reference materials are:

Catalogues of the producers

Websites e.g. IRMM website or http://www.erm-crm.org/

Databases e.g. Comar http://www.comar.bam.de/

Dedicated websites such as http://www-naweb.iaea.org/nahu/nmrm

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