TO NORMALIZE OR NOT TO NORMALIZE - FAT IS THE QUESTION

Concentrations of lipophilic contaminants in biota are frequently corr ected for variation in tissue lipid content. Usually, this correction is accomplished by dividing tissue contaminant concentration by lipid concentration to form lipid-normalized data, This ratio-based approach is satisfactory when contaminant concentration varies in direct propo rtion to lipid content. However, when such a relationship does not exi st, erroneous conclusions may be reached. Recent research has emphasiz ed the potential shortcomings of the use of ratio variables. We demons trate the importance of considering these shortcomings when lipid-norm alizing data. Three examples are presented, and an alternative approac h based upon the use of analysis of covariance (ANCOVA) is suggested.