Repeated-dose 90-day Oral Toxicity Studies on Whole ... - Europabio

4. Measures of variation
• Given that effect sizes are expressed in percentage terms, the most
appropriate measure of variation is the coefficient of variation (CV).
• Cage was regarded as the ExpU; CV at the cage level is dependent
on the number of rats per cage.
• Evidence of differences in CV between males and females was
detected.
• For each of the endpoints considered, CV’s for a given gender and
number of rats per cage were found to be fairly consistent across
studies.
– Also, no evidence to suggest that CV differed between corn and
soy-based diets.
• So, for each endpoint, an average CV was generated for each
gender / housing policy combination, to be used in subsequent
power calculations.
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