Improved estimates of floating absolute risk.

Floating absolute risks are an alternative way of presenting relative risk estimates for polychotomous risk factors. Instead of choosing one level of the risk factor as a reference category, each level is assigned a 'floated' variance which describes the uncertainty in risk without reference to another level. In this paper, a method for estimating the floated variances is presented that improves on the previously proposed 'heuristic' method. The estimates may be calculated iteratively with a simple algorithm. A benchmark for validating the floated variance estimates is also proposed and an interpretation of floating confidence intervals is given. Copyright 2004 John Wiley & Sons, Ltd.