Statistical Methods For Mineral Engineers -

$$ \ln\left(\frac{p}{1-p}\right) = \beta_0 + \beta_1 X_1 + ... + \beta_n X_n $$

Where $p$ is the probability of recovery (the metal reporting to concentrate). Many flotation recovery curves follow a sigmoidal shape. The Hill equation (borrowed from biochemistry) models recovery as a function of residence time: Statistical Methods For Mineral Engineers

If $X$ is the vector of measured variables and $V$ is the variance-covariance matrix of measurements, we find the adjusted values $\hat{X}$ that minimize: $$ \ln\left(\frac{p}{1-p}\right) = \beta_0 + \beta_1 X_1 +

Where $\gamma(h)$ is the semivariance, $h$ is the lag distance, and $Z$ is the grade. $h$ is the lag distance

For mineral engineers, this is revolutionary.

$$ (X - \hat{X})^T V^{-1} (X - \hat{X}) $$