# Statistics - Generalized Linear Models (GLM) - Extensions of the Linear Model

### Table of Contents

## 1 - About

The Generalized Linear Model is an extension of the linear model that allows for lots of different, **non-linear** models to be tested in the context of regression.

GLM is the mathematical framework used in many statistical analyses such as:

- analysis of variance (for categorical predictors)
- and mediation.

GLM is a supervised algorithm with a classic statistical technique (Supports thousands of input variables, text and transactional data) used for:

- and/or Regression

GLM implements:

- logistic regression for classification of binary targets
- and linear regression for continuous targets.

Confidence bounds are supported with a

- GLM classification for prediction probabilities.
- GLM regression for predictions.

## 2 - Articles Related

## 3 - Assumptions

The General Linear model has two main characteristics:

- Linear: linear relationships between the predictors and the outcome measure.
- Additive: the effects of each predictor are additive with one another

That doesn't mean that the GLM can't handle non-additive or non-linear effects.

Removing the additive assumption:

- interactions and

GLM can accommodate such non-additive or non-linear effects with:

- Transformation of variables: in order to make them linear
- Adding interaction terms or moderation terms: in order to do a moderation analysis and test for non-additive facts.

## 4 - Methods

Methods that expand the scope of linear models and how they are fit:

- Classification problems: logistic regression, support vector machines
- Non-linearity: kernel smoothing, splines and generalized additive models; nearest neighbour methods.
- Interactions: Tree-based methods, bagging, random forests and boosting (these also capture non-linearities)
- Regularized fitting: Ridge regression and lasso. These have become very popular lately, especially when we have data sets where we have very large numbers of variables–so-called wide data sets, and even linear models are too rich for them, and so we need to use methods to control the variability.