Mean Monte Carlo Results

Question

Hi,

The estimated mean of my Monte Carlo simulation, unfortunately, differs from the result calculated by "Quick results". The results of the MC mean approach 3.0 kgCO2e instead of 2.6 kgCO2e.

How is it possible that a deviation between these two values occurs? Do you have any idea why these two values are different in my case?

Thanks for your support!

Answer 1

That's a property of the mean (i.e. arithmetical average). Large positive outliers lead typically to higher arithmetical mean values, especially if the probability distribution is asymmetrical and non-negative, as the lognormal distribution used in ecoinvent; the median is more "resilient" to these outliers, see e.g. https://en.wikipedia.org/wiki/Arithmetic_mean.