% This is lecture no. 2 of MH4512/: Clinical Trials.

\chapter{Mixed Effects Model}%
\label{cha:mixed_effects_model}

\section{Motivation}%
\label{sec:motivation}

As mentioned in \cref{cha:introduction}, clinical trials involve measurements of the effects of a treatment on human subjects.
The end goal is to be able to say something specific about the treatment---whether it is safer than another treatment, whether it is faster acting compared to another treatment, or even whether it is more effective than a placebo.

We want to be able to say these things with a certain \textbf{level of confidence}.
That's a statistical term which comes with a technical definition, but it arises from the intent of those words.
For example, let's say that a clinical trial was conducted to test whether a drug is effective in making people fall asleep quickly.
The trial recruited a total of 40 healthy individuals, and randomly split them into two groups of 20.
