In applied statistics, optimal estimation is a regularized matrix inverse method based on Bayes' theorem. It is used very commonly in the geosciences, particularly for atmospheric sounding. A matrix inverse problem looks like this:
The essential concept is to transform the matrix, A, into a conditional probability and the variables, x → {\displaystyle {\vec {x}}} and y → {\displaystyle {\vec {y}}} into probability distributions by assuming Gaussian statistics and using empirically-determined covariance matrices.