4.1 Introduction4.2 Mathematical Definition of a Stochastic Process4.3 Two Classes of Stochastic Processes: Strictly Stationary and Weakly Stationary4.4 Mean, Correlation, and Covariance Functions of Weakly Stationary Processes4.5 Ergodic Processes4.6 Transmission of a Weakly Stationary Process through a Linear Time-invariant Filter4.7 Power Spectral Density of a Weakly Stationary Process4.8 Another Definition of the Power Spectral Density4.9 Cross-spectral Densities4.10 The Poisson Process4.11 The Gaussian Process4.12 Noise4.13 Narrowband Noise4.14 Sine Wave Plus Narrowband Noise4.15 Summary and Discussion