\subsection{Ranking}
\label{ranks}

\figref{results_ranks} shows the ranking of each visual \factor{Hand} rendering for the \factor{Push} and \factor{Grasp} tasks.
Friedman tests indicated that both ranking had statistically significant differences (\pinf{0.001}).
Pairwise Wilcoxon signed-rank tests with Holm-Bonferroni adjustment were then used on both ranking results (\secref{metrics}):

\begin{itemize}
  \item \response{Push task ranking}: \level{Occlusion} was ranked lower than \level{Contour} (\p{0.005}), \level{Skeleton} (\p{0.02}), and \level{Mesh} (\p{0.03});
    \level{Tips} was ranked lower than \level{Skeleton} (\p{0.02}).
    This good ranking of the \level{Skeleton} rendering for the Push task is consistent with the Push trial results.
  \item \response{Grasp task ranking}: \level{Occlusion} was ranked lower than \level{Contour} (\p{0.001}), \level{Skeleton} (\p{0.001}), and \level{Mesh} (\p{0.007});
    No Hand was ranked lower than \level{Skeleton} (\p{0.04}).
    A complete visual hand rendering seemed to be preferred over no visual hand rendering when grasping.
\end{itemize}

\begin{subfigs}{results_ranks}{Boxplots of the ranking for each visual hand rendering. }[
    Lower is better.
    Pairwise Wilcoxon signed-rank tests with Holm-Bonferroni adjustment: ** is \pinf{0.01} and * is \pinf{0.05}.
  ][
  \item Push task ranking.
  \item Grasp task ranking.
  ]
  \subfig[0.4]{results/Ranks-Push}
  \subfig[0.4]{results/Ranks-Grasp}
\end{subfigs}