Statistical assessment of bioassay data

and other nonlinear regression problems

with the free software R

Workshop by EWRS Education and Training Working Groups
Sunday 7th of October 2007, 8:30-16:30

Course Description

Herbicides are designed to kill plants and their selective use in crops is a question of dose. Consequently, use of dose-response curves is fundamental to understanding herbicide selectivity and efficacy. This principle can be extended to other branches of weed management, e.g. allelopathy, flame weeding, weed steaming, physical control, laser cutting and radiation and weed crop competition. Dose-response curves, germination curves, and competition models are genuine non-linear. The way they are summarized varies and often depends on tradition and/or available statistical software rather than theoretical considerations of the best way to exploit the information contained in the data.

The aim of the course is to make participants able to succinctly assess toxicity on the basis of proper choice of dose-response models and compare dose-response curves statistically using the free software programme R and a specific developed extension package, drc, developed for weed scientists and freely downloadable at URL: www.bioassay.dk. Additionally, the package drc can also be used to fit germination curves and user-defined functions, for example competition models.

Course Content

• The concept of nonlinear response curves
• Installation of R and how to work with the programme.
• Fitting and comparing response curves, e.g.: discrete versus gradual endpoints, relative versus raw data, upper and lower limits, measurement of efficacy and index of selectivity of herbicides, competitive ability, germination ability and bioassay design, heterogeneity of variance.
• Working on handout data or, preferentially, own data.

Fee and Duration

Eight hours; €60.0

Participants

Graduates and postgraduate students, weed scientists in public and private institutions.
There will be a maximum of 15 attendants on a first-come, first-served basis.

If you are interested in participating in this course, please note your request in the appropriate box on the Payment and Accommodation Form, then print, sign and fax(only!) to us.

Course Material

Course material will be uploaded at the www.bioassay.dk website one week prior to the workshop.

Prerequisite

Basic knowledge of statistics, including regression analysis, would be preferable.

updated September 9, 2007