Preditox School 2021 : ECOTOXICOLOGY & PREDICTIVE MODELLING

Preditox School 2021 : ECOTOXICOLOGY & PREDICTIVE MODELLING

INTRODUCTION TO R SOFTWARE

Participants will be introduced to R programming and to basic statistics in R, based on concrete toxicity test data. R is a language and environment for statistical computing and graphics (http://cran.r-project.org/). It provides a wide variety of statistical and graphical techniques. It is highly extensible through a great number of packages dedicated to specific topics. Participants will explore the most useful ones for ecotoxicity data analysis.

DOSE-RESPONSE MODELING

There is today a large consensus recognizing ECx as an appropriate index of toxicity as far as data are sufficient and properly fitted with suitable models. Nevertheless, the choice of the appropriate model is not straightforward: both the deterministic and the stochastic parts must be appropriately chosen in accordance with the type of experimental data (quantal data e.g. for survival, continuous data e.g. for growth or count data e.g. for reproduction). Participants will be introduced to up-to-date methods, especially generalized non-linear models and TKTD models such as GUTS models.

BAYESIAN INFERENCE

Bayesian inference has showed its usefulness in ecotoxicology as a relevant alternative when estimating parameters of models, simultaneously fitted to different types of data. Within the Bayesian framework, parameter estimation requires three steps:

• model building, defining logical and stochastic links between parameters and variables;

• prior distributions of all parameters reflecting the state of knowledge available before analysing the data;

• posterior distributions of all parameters computed using the Bayes’ theorem, combining priors and observations. Bayesian inference is very flexible and makes the use of generalized non-linear and TKTD models very easy. Participants will be trained step-by-step with the JAGS software (http://mcmc-jags.sourceforge.net/).

Registration fees include attendance to the school (including course material), coffee breaks, breakfasts, lunches, dinners and accommodation (from July 4 evening to July 10 morning, 2021).