---
title: "Course Introduction"
author: "Dr. Jin Zhou @ UCLA"
date: "Apr 4, 2023"
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subtitle: Biostat 200C
---

## Course webpages

- Github site: <https://ucla-biostat-200c.github.io/2023spring/>
  + slides, hw, announcements 

- Burinlearn: <https://bruinlearn.ucla.edu/courses/160230>
  + announcements and hw submissions





## What's this course about?

-   In 200B, we learn the linear models in the form $$
    y = \beta_0 + \beta_1 x_1 + \cdots + \beta_p x_p + \epsilon, 
    $$ where
    1.  $y$ is a continuous *response variable* (or *dependent variable*),\
    2.  $x_1, \ldots, x_p$ are *covariates* (or *predictors*, or *independent variables*), and\
    3.  $\epsilon$ is the *error term* and assumed to be normally distributed and independent among observations.
-   In 200C, we generalize the linear models in three directions.
    1.  **Generalized linear models (GLMs)** handles nonnormal responses, $y$. \
        * binary response (disease or not)
        * proportions
        * counts
    2.  **Mixed effects models** relaxes the independence assumption of the error term and allows correlation structure in $\epsilon$.\
        * Some data has a grouped, nested or hierarchical structure. 
        * Repeated measures, longitudinal and multilevel data 
    3.  **Nonparametric regression models** (GAM, trees, neural networks) allow nonlinearity in the effects of predictors $x$ on responses.

## Course description

-   Read [syllabus](https://ucla-biostat-200c.github.io/2023spring/syllabus/syllabus.html) and [schedule](https://ucla-biostat-200c.github.io/2023spring/schedule/schedule.html) for a tentative list of topics and course logistics.

-   Teaching philosophy. Usually a GLM course is taught on blackboard/whiteboard with mostly math derivations. In this course, I will start from R code and then explain the theory behind it.