A Logical Introduction to the Components of the Overall Estimation Error

Before introducing the various components of the Overall Estimation Error OEE , it is beneficial to proceed with an introduction to the fundamental notion of heterogeneity. To find out how it is defined, and to clearly differentiate this notion from the notion of homogeneity. It does not involve a great deal of research to find out that homogeneity is often a relative concept. If we look at a pile of fine sand from a distance, the pile may appear homogeneous; however, we know that as we come closer toward the pile and finally look at it under a magnifying glass, we realize that the homogeneity was only an illusion. The only reality is a state of great heterogeneity when each individual grain is examined showing differences in sizes, colors, compositions, shapes, densities, opacities, porosities, etc. It is not long before one wonders whether homogeneity is only a limit case rarely encountered. We indeed live inside a heterogeneous world. And if we try to measure this heterogeneity, we intuitively find that the zero of heterogeneity is homogeneity, just a limit case.