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1 July 2007 Utilizing R Software Package for Dose-Response Studies: The Concept and Data Analysis
Stevan Z. Knezevic, Jens C. Streibig, Christian Ritz
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Advances in statistical software allow statistical methods for nonlinear regression analysis of dose-response curves to be carried out conveniently by non-statisticians. One such statistical software is the program R with the drc extension package. The drc package can: (1) simultaneously fit multiple dose-response curves; (2) compare curve parameters for significant differences; (3) calculate any point along the curve at the response level of interest, commonly known as an effective dose (e.g., ED30, ED50, ED90), and determine its significance; and (4) generate graphs for publications or presentations. We believe that the drc package has advantages that include: the ability to relatively simply and quickly compare multiple curves and select ED-levels easily along the curve with relevant statistics; the package is free of charge and does not require licensing fees, and the size of the package is only 70 MB. Therefore, our objectives are to: (1) provide a review of a few common issues in dose-response-curve fitting, and (2) facilitate the use of up-to-date statistical techniques for analysis of dose-response curves with this software. The methods described can be utilized to evaluate chemical and non-chemical weed control options. Benefits to the practitioners and academics are also presented.

Stevan Z. Knezevic, Jens C. Streibig, and Christian Ritz "Utilizing R Software Package for Dose-Response Studies: The Concept and Data Analysis," Weed Technology 21(3), 840-848, (1 July 2007).
Received: 29 September 2006; Accepted: 1 April 2007; Published: 1 July 2007

experimental design
nonlinear regression
weed dry matter
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