The Organisation for Economic Co-operation and Development (OECD) is an inter-governmental organisation which aims to facilitate global trade and economic development. A key area is the development of global standards. The OECD’s Good Laboratory Practice (GLP) scheme is an example of such standards: It provides guidance on all aspects related to non-clinical health and environmental…
In a previous blog, we looked at fitting dose-response models to quantal data in ecotoxicology scenarios. To recap, quantal data refers to data where the response variable takes a binary value. A number of organisms are exposed to a dose of test substance and then after a set period of time the number exhibiting a…
Recently our team at Quantics were working on an analysis for an ecotoxicology client which called for us to use the Jonckheere-Terpstra test for ordered differences which is recommended by the OECD in their guidance document on statistical analysis of ecotoxicity data. We were subsequently asked to explain how it was used and we thought…
In ecotoxicology statistics there are three main types of data: Continuous data can take any numerical value over a range (e.g. weight), while discrete data take a finite number of values (e.g. colour). Quantal data, the focus of this post, can take only one of two values (e.g. alive/dead or mobile/immobile) and are often recorded…
Ecotoxicity tests are experiments performed to evaluate the toxicity of a test substance in order to predict the effect on natural populations. There are many different types of test, but the general principle is that organisms are exposed to different concentrations or doses of a test substance, with at least one control group that is…