1 EM optimization method 1.1 EM algorithm 1.2 Convergence 1.3 Usage in exponential families 1.4 Usage in finite normal mixtures 1.5 Variance estimation 1.5.1 Louis method 1.5.2 SEM algorithm 1.5.3 Bootstrap method 1.5.4 Empirical Information 1.6 EM Variants 1.6.1 Improving the E step 1.6.2 Improving the M step 1.7 Pros and Cons