Question

How does openLCA calculate uncertainty values?

The corresponding (ecoinvent) data quality system values are:

I suppose "σg" is the geometric mean. However, MS Excel returns `=GEOMEAN(1.05,1.1,1.5,1.1,1.2)` = 1.179911502.

How do I reproduce the given uncertainty value?

Answer 1

Hey!

Check How to interpret the uncertainty fields in ecoinvent?

This helped me when I was stuck with a similar problem. Perhaps, it will help you too. There is also an excel file linked at the bottom of the answer to play around and understand things based on your use case.

Best regards,

Vineet

Comments

you are right, but I replied in addition since we have indeed a mistake in the value as it is shown now (and will fix that)

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Thank you both for your responses!

Answer 2

Hi, thank you for your question, it is not the mean but the standard deviation, quite some background is provided in our older project report (https://www.greendelta.com/wp-content/uploads/2017/03/Pedigree_report_final_May2012.pdf) - but you are right, we need to take the root of the amount openLCA lists here so far (or, instead, state that this is not sigma_g but the geometric variance) but we rather go for the first option. Therefore, thank you!

Comments

Hi, I would like to understand if even if the software shows the value of the squared deviation in the field named as "standard deviation", it does the uncertainty calculations, through the Monte Carlo analysis, correctly. Or if we, users, would need to correct the value of the "geometric standard deviation" field, manually inserting the root of the squared deviation value there (without using that "Use as uncertainty value" path in the "Pedigree matrix" tab.