\documentclass[../Main.tex]{subfiles} \begin{document} %\subsection{Data Exploration} %TODO: fill this out later. %look at trial \subsection{Model Fitting} In this section we examine the results from fitting the econometric model using mc-stan (\cite{mc-stan}) through the rstan (\cite{rstan}) interface. %describe The model was based on the hierarchal logistic regression model presented in the Stan Users Guide (\cite{mc-stan}), and was run with 2,500 warmup iterations and 2,500 sampling iterations in six chains. There were various issues, including 160 divergent transitions and the R-hat measure was 1.49. Overall these suggest that the econometric model is incorrect as written or requires reparameterization. %TODO: and info about how I learned about these diagnostics % \subsubsection{Diagnostics} % %Examine trank plots % To identify which parameters were problematic, I first looked at trace rank % histograms. % Under idea circumstances, each line (representing a chain) should exchange % places with the other lines frequently. % In both \cref{fig:mu_trank} and \cref{fig:sigma_trank}, most parameters seem % to mix well but there are a couple of exceptions. % This warrants further investigation. % % \begin{figure}[H] % \includegraphics[width=\textwidth]{../assets/img/mu_trank.png} % \caption{Trace Rank Histogram: Mu values} % \label{fig:mu_trank} % \end{figure} % % \begin{figure}[H] % \includegraphics[width=\textwidth]{../assets/img/sigma_trank.png} % \caption{Trace Rank Histogram: Sigma values} % \label{fig:sigma_trank} % \end{figure} % % %Take a look at batman and points for mu % In the case of the Mu values, a parallel coordinates plot % doesn't seem to indicate any parameters as likely candidates % for causing the issues with divergent transitions. % \begin{figure}[H] % \includegraphics[width=\textwidth]{../assets/img/mu_batman.png} % \caption{Parallel Coordinate Plot: Mu values} % \label{fig:mu_batman} % \end{figure} % Note that at each parameter, there is some level of dispersion between % values that diverged. % % On the other hand, in the parallel coordinates plot for sigma values, % it appears that most divergent transitions occur with values of % sigma[1], sigma[3], sigma[6], and sigma[7] close to zero. % \begin{figure}[H] % \includegraphics[width=\textwidth]{../assets/img/sigma_batman.png} % \caption{Parallel Coordinate Plot: Sigma values} % \label{fig:sigma_batman} % \end{figure} % Overall this suggests that there is an issue with the specification % of the covariance structures of the hyperparameters. % % Additional evidence that the covariance structure is incorrect comes from % plotting pairs of parameter values and examining the chains with divergent % transitions. % % \begin{figure}[H] % \includegraphics[width=\textwidth]{../assets/img/sigma_pairs_5-9.png} % \caption{Parameter Pairs plots: Sigma[5] through Sigma[9]} % \label{fig:sigma_pairs_5-9.png} % \end{figure} % From this we can see that divergent pairs are highly correlated with the cases % where sigma[6] or sigma[7] are equal to zero. % This has an impact on the shape of both of those estimated parameters, causing % both to be bimodal. \subsection{Interpretation} The key results so far are related to the distribution of differences in $p$. In figure \ref{fig:pred_dist_dif_delay} we see that there while most trials do not see any increased risk from a delay in closing enrollment, there is a small group that does experience this. \begin{figure}[H] \includegraphics[width=\textwidth]{../assets/img/current/pred_dist_diff-delay} \caption{} \label{fig:pred_dist_diff_delay} \end{figure} Figure \ref{fig:pred_dist_dif_delay2} shows how this varies across disease categories \begin{figure}[H] \includegraphics[width=\textwidth]{../assets/img/current/pred_dist_diff-delay-group} \caption{} \label{fig:pred_dist_dif_delay2} \end{figure} We can also examine the direct effect from adding a single generic competitior drug. \begin{figure}[H] \includegraphics[width=\textwidth]{../assets/img/current/pred_dist_diff-generic} \caption{} \label{fig:pred_dist_diff_generic} \end{figure} Figure \ref{fig:pred_dist_dif_generic2} shows how this varies across disease categories \begin{figure}[H] \includegraphics[width=\textwidth]{../assets/img/current/pred_dist_diff-generic-group} \caption{} \label{fig:pred_dist_dif_generic2} \end{figure} \end{document}