How sensitive is the indicator to population changes in one or a few species?
The indicator uses the logarithm of the indices of species, and taking the logarithm usually dampens the effect of changes in one or a few species on the indicator substantially. Also criteria used for decision whether a species is to be included in an indicator are aimed to prevent too much effect of a single species on it. Nevertheless, if the indicator would contain only a handful of species, population changes in one or a few species may affect the indicator considerably. It is possible – and useful – to test statistically whether the change in the indicator is only based on one or a few deviating species or reflects an overall change of the group.
Learn more in Methods, chapter 4. Quality control.