In the forties, the index approach to measure segregation for powder mixtures was introduced. Since that time, several researchers have introduced new indices in an effort to improve this approach continually for the determination of mixture segregation. However, there are two major drawbacks of all current indices that make them unattractive as measures of segregation. First, these indices can vary for reasons other than segregation. The second drawback is the inability to determine if the calculated values of these indices are significant while controlling the probability of making incorrect conclusions. In this article a measure of segregation is proposed that is not subject to these limitations. In addition, a theoretical evaluation is given of current indices and the proposed approach. The conclusions of this evaluation are illustrated and confirmed by a Monte Carlo simulation study.