Novel, non-destructive material analysis methods provide a useful alternative to conventional chemical assay techniques, allowing rapid or real-time determination of ore grade with minimal sample preparation. Particularly when used for quantitative applications such as resource evaluation, grade control or metal accounting, it is important to establish whether new and old results can be used interchangeably.

The combination of heavily skewed grade distributions and large sampling errors lead to significant biases when conventional metrics, such as correlation coefficients, analysis of variance (ANOVA), regressions and Tukey mean-difference or Bland-Altman plots are used to compare two assay methods. We show how these metrics can be modified to produce unbiased estimates of the quality of agreement between different assay results and introduce a procedural approach for validating new analysis methods.

PhotonAssay is a recently introduced method for the measurement of gold in ore samples. We illustrate the application of our new metrics through the comparison of PhotonAssay and fire-assay grade results on a variety of ore types.

新颖的非破坏性材料分析方法为常规化学分析技术提供了一种有用的替代方法，可在最少的样品制备过程中快速或实时确定矿石品位。特别是在用于资源评估，品位控制或金属会计等定量应用时，确定新旧结果是否可以互换使用非常重要。

当常规指标（例如相关系数，方差分析（ANOVA），回归和Tukey均差或Bland-Altman图）用于比较两种测定方法时，严重偏斜的等级分布和较大的采样误差的组合会导致明显的偏差。我们展示了如何修改这些指标以产生不同测定结果之间的协议质量的无偏估计，并介绍一种用于验证新分析方法的程序方法。

PhotonAssay是最近引入的一种用于测量矿石样品中金的方法。我们通过比较PhotonAssay和火​​法等级结果对各种矿石的类型，说明了我们新指标的应用。