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D-OPTIMAL EXPERIMENTAL DESIGNS TO TEST FOR DEPARTURE FROM ADDITIVITY IN A FIXED-RATIO MIXTURE RAY.
Citation:
COFFEY, T., C. GENNINGS, J. E. SIMMONS, AND D. W. HERR. D-OPTIMAL EXPERIMENTAL DESIGNS TO TEST FOR DEPARTURE FROM ADDITIVITY IN A FIXED-RATIO MIXTURE RAY. TOXICOLOGICAL SCIENCES. Society of Toxicology, RESTON, VA, 88(2):467-476, (2005).
Impact/Purpose:
To increase the statistical power for fixed-ratio experimental designs for additivity
Description:
Humans are exposed to mixtures of environmental compounds. A regulatory assumption is that the mixtures of chemicals act in an additive manner. However, this assumption requires experimental validation. Traditional experimental designs (full factorial) require a large number of experimental observations and resources. Fixed-ratio ray designs allow testing for departures from additivity for defined ratios of chemicals (similar to those found in the environment). This paper describes methodology to increase the statistical power for fixed-ratio experimental designs. The increased power allows stronger conclusions to be drawn about any deviations from additivity that may be observed, and conserves valuable experimental resources. Use of such methods will increase the validity of risk assessment conclusions regarding the additivity (or lack thereof) for environmental mixtures of chemicals.