Conditional Expectation Definition $L^p$ Spaces Definition Closed Form Formula for the Ridge Regression Estimator Probability & Statistics Hilbert Projection Theorem for Closed Linear Subspaces of $L^2$ Probability & Statistics Equality Condition in the Gauss-Markov Theorem Probability & Statistics Wiener's Theorem Brownian Motion Threshold Events Are Events Probability Theory Tail Integral Formula Probability Theory Discrete Convolution Formula Probability Theory Factorisation Criterion for Independence Probability Theory Probability & Statistics Area