Hi, what is the reasonable cut-off percentage of species contribution for SIMPER analysis? Most papers I've seen are at 90%, but there are those at 60%. Is the value determined by the author or is there a specific rule to this?
Thank you in advance.
1. A certain area agricultural professional took soil sample with container having volume of 100 cm3 and 500 gm mass. The mass of the soil sample was 700 gm. He placed it in an oven dry for 24 hours at 105 oc temperature. The oven dry mass of the soil sample was 630 gm.
A. Calculate the bulk density.
B. Calculate the porosity. Consider particle density as 2.65 gm/cm3.
C. Interpret your result.
D. Estimate the textural class based on your result.
No idea what those 'answers' are about. Anyway, to answer the SIMPER question there is no set limit or guidance, it is a choice to be made by the investigator and is really just a matter of convenience. If you have, say, 300 species in your dataset and do not apply a cut-off each of the results tables (if you have N groups then you will have N within-group tables and (N*N-1)/2 pairwise tables) will have all 300 species in them. This would make them very unwieldy and most species will be providing very little usable information. The cut-off is chosen as a trade-off between getting a manageable amount of information and getting an understanding of which species contribute to the groups' structure. With very large datasets (e.g. metagenomic data with thousands of OTUs) it may be necessary to have a low cut-off in the regions of 10 or 20% just to be able to see what's going on. The default in Primer is 70% I think, which would be fine for most ecological datasets with a couple of hundred species.
Nur Syuhada Nazron It can be decided by the authors, but logically. I support the answer given by Paul Somerfield.
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