Their geometrical interpretations are as follows (Table 1). The data for H01L2D lie on an ℝm−1 iso-sphere, and the associated test for (5a) is executed on the radius of the ℝm−1 iso-sphere, leading to no geometrical distortion (but not necessarily true statistically). On the other hand, the data for H02L2D are on two ℝm−1 iso-sphere surfaces, and the associated test for (5b) acts on the radius difference between the two ℝm−1 iso-spheres, resulting a detection failure when the two HDR curves have roughly the same radius.