Problems with Ratio Analysis in Nutritional Studies

where C is the energy consumed, F is the energy content of the faeces and U is the energy content of the nitrogenous wastes (e.g. urine). Similar indices now appear in many entomological papers (Waldbauer 1968; Slansky & Scriber 1982, 1985). Ratios remain an ambivalent issue in biology, as is illustrated in the following quotation: '... there are some serious drawbacks to the use of ratios and percentages in statistical work... [but] ... we should emphasise that ratios may be the only meaningful way to interpret and understand certain types of biological problems' (Sokal & Rohlf 1981). Here I use the nutritional indices ADC and MEC to examine some of the issues involved in deciding on whether to analyse ratios or the parent variables. I conclude that there are considerable costs associated with the use of ratios and little justification for the claim that they provide information not available through analysis of the measured variables.