search for: llod

Ah.... LOD's, typically LLOD's ("lower limits of detection"). Disclaimer: I am *NOT* in any sense an expert on such matters. What follows are just some comments based on my personal experience. Please filter accordingly. Also, while I kept it on list as Martin suggested it might be useful to do so, most folks pr...

...ps://gist.github.com/jdnewmil/99301a88de702ad2fcbaef33326b08b4 OP perhaps posting a link here to your question posed wherever you end up with it will help shorten this thread. On January 22, 2024 12:23:20 PM PST, Bert Gunter <bgunter.4567 at gmail.com> wrote: >Ah.... LOD's, typically LLOD's ("lower limits of detection"). > >Disclaimer: I am *NOT* in any sense an expert on such matters. What follows >are just some comments based on my personal experience. Please filter >accordingly. Also, while I kept it on list as Martin suggested it might be >useful to...

On Mon, 22 Jan 2024, Martin Maechler wrote: > I think it is a good question, not really only about geo-chemistry, but > about statistics in applied sciences (and engineering for that matter). > John W Tukey (and several other of the grands of the time) had the log > transform among the "First aid transformations": > > If the data for a continuous variable must all be

...sense to compute the arithmetic mean. Results are usually reported as some quantile (median or 90%); alternatively, one computes the geometric mean. ### Ecology /Environmental Chemistry I suppose that certain chemicals may be generated/released in the environment through a non-linear process. The LLOD may also play a role, but may NOT be the main reason. If the generating process is exponential, then the arithmetic mean would strongly skew the results (also inconsistently based on season, particular year, etc - the generating processes may differ). ### Harmonic Mean Did not encounter it often:...