🎉 75% of content is free forever — Unlock Premium from $10/mo →
CW
Search courses…
💼 Servicesℹ️ About✉️ ContactView Pricing Plansfrom $10

Probability Theory & Bayesian Inference for Machine Learning

AI/ML PremiumProbability Theory & Bayesian Inference🟢 Free Lesson

Advertisement

Probability Theory & Bayesian Inference for Machine Learning

Module: AI/ML Premium | Difficulty: PhD Level | Prerequisites: Measure Theory, Linear Algebra


1. Measure-Theoretic Probability

1.1 Probability Spaces

1.2 Random Variables and Distributions

Probability HierarchyΩ (Sample Space)All possible outcomesΩ = {ω₁, ω₂, ...}ω ∈ Ω: elementary eventF (σ-algebra)Event spaceClosed under complementClosed under countable unionP (Probability)P: F → [0,1]P(Ω) = 1Countably additiveRandom Variable X: Ω → ℝMeasurable function from Ω to ℝX(ω) = value assigned to outcome ωDistribution Pₓ: P(B) = P(X⁻¹(B)) — Pushforward measure on (ℝ, B(ℝ))

2. Expectation and Variance

2.1 Expected Value

2.2 Variance and Covariance

2.3 Important Inequalities

Probability Distributions for MLDiscrete DistributionsBernoulli(p): P(1)=pBinomial(n,p): C(n,k)pᵏ(1-p)ⁿ⁻ᵏPoisson(λ): λᵏe⁻λ/k!Categorical(p₁,...,pₖ)ML: Classification targets, Discrete latent variablesContinuous DistributionsN(μ,σ²): GaussianExp(λ): λe⁻λˣBeta(α,β): Conjugate priorDirichlet(α): Multi-classML: Continuous latent variables, Priors, Generative modelsExponential Family (Key for ML)p(x|η) = h(x) exp(ηᵀT(x) - A(η))η: natural parameter, T(x): sufficient statistic, A(η): log-partitionIncludes: Gaussian, Bernoulli, Categorical, Poisson, Beta, Dirichlet, GammaProperty: E[T(X)] = ∇A(η), Cov[T(X)] = ∇²A(η)

3. Bayesian Inference

3.1 Bayes' Theorem

3.2 Conjugate Priors

Bayesian Inference ProcessPrior P(θ)Before seeing dataEncodes beliefsBeta(α₀, β₀)N(μ₀, σ₀²)Dirichlet(α₀)Likelihood P(D|θ)Data generation modelP(xᵢ|θ)Bernoulli, Gaussian, etc.Product over data pointsP(D|θ) = ∏P(xᵢ|θ)Posterior P(θ|D)Updated beliefs∝ Prior × LikelihoodBeta(α₀+Σxᵢ, β₀+n-Σxᵢ)N(μₙ, σₙ²)More data → sharper×=Bayesian Decision Theory0-1 Loss: L(a,y) = 𝟙[a≠y]Squared: L(a,y) = (a-y)²Absolute: L(a,y) = |a-y|Risk R(a) = 𝔼[L(a,θ)] = ∫ L(a,θ) P(θ|D) dθPosterior mean: a* = argmin R(a) for squared lossPosterior median: a* = argmin R(a) for absolute loss

4. Information Theory

4.1 Entropy and KL Divergence

4.2 Mutual Information

Information Theory for MLEntropy H(X)Uncertainty measureH(X) = -Σ p(x) log p(x)Max for uniform distributionBits (log₂) or nats (ln)KL DivergenceAsymmetric distanceD_KL(P||Q) = Σ p log(p/q)D_KL(P||Q) ≥ 0 (Gibbs)Not a true metric (asymmetric)Mutual InformationDependency measureI(X;Y) = H(X) - H(X|Y)I(X;Y) = D_KL(P_XY || P_X P_Y)I(X;Y) = I(Y;X) ≥ 0Applications in MLFeature SelectionVAE Loss (ELBO)Decision TreesVariational Inference • ICA • Information Bottleneck • Contrastive Learning

5. Exponential Families

5.1 Definition

5.2 Properties


6. Variational Inference

6.1 Evidence Lower Bound (ELBO)

Variational Inference FrameworkP(θ|D)True PosteriorOften intractableP(D|θ)P(θ)/P(D)Normalizing constant unknownq_φ(θ)Approximate PosteriorTractable familyGaussian, Mean-field, etc.Parameters φ optimizedD_KLELBO(φ)= 𝔼_q[log P(D|θ)]- D_KL(q_φ(θ) || P(θ))Lower bound on log P(D)Maximize w.r.t. φVariational Inference vs MCMCVI: Optimization (fast, approximate)MCMC: Sampling (slow, exact)VI scales to large datasets • MCMC provides uncertainty estimates

7. Monte Carlo Methods

7.1 Importance Sampling

7.2 Markov Chain Monte Carlo (MCMC)


8. Bayesian Deep Learning

8.1 Uncertainty Quantification

8.2 Types of Uncertainty

TypeSourceMethod
AleatoricInherent noiseHeteroscedastic models
EpistemicLimited dataMC Dropout, SWAG
ModelWrong architectureBayesian model comparison

Summary

ConceptFormulaApplication
Bayes' TheoremParameter estimation
KL DivergenceVariational inference
ELBOApproximate inference
EntropyInformation theory

Research Frontier: Neural processes combine neural networks with Gaussian processes, enabling amortized Bayesian inference with learned priors.

Need Expert AI/ML Premium Help?

Get personalized tutoring, project support, or professional consulting.

Advertisement