\subsection{Push Task}
\label{push}

\paragraph{Completion Time}

On the time to complete a trial, there were two statistically significant effects:
\factor{Positioning} (\anova{4}{1990}{3.8}, \p{0.004}, see \figref{results/Push-CompletionTime-Location-Overall-Means}) %
and \factor{Target} (\anova{1}{1990}{3.9}, \p{0.05}).
\level{Fingertips} was slower than \level{Proximal} (\percent{+11}, \p{0.01}) or \level{Opposite} (\percent{+12}, \p{0.03}).
There was no evidence of an advantage of \level{Proximal} or \level{Opposite} on \level{Nowhere}, nor a disadvantage of \level{Fingertips} on \level{Nowhere}.
Yet, there was a tendency of faster trials with \level{Proximal} and \level{Opposite}.
The \level{LB} target volume was also faster than the \level{LF} (\p{0.05}).

\paragraph{Contacts}

On the number of contacts, there was one statistically significant effect of
\factor{Positioning} (\anova{4}{1990}{2.4}, \p{0.05}, see \figref{results/Push-Contacts-Location-Overall-Means}).
More contacts were made with \level{Fingertips} than with \level{Opposite} (\percent{+12}, \p{0.03}).
This could indicate more difficulties to adjust the virtual cube inside the target volume.

\paragraph{Time per Contact}

On the mean time spent on each contact, there were two statistically significant effects of
\factor{Positioning} (\anova{4}{1990}{11.5}, \pinf{0.001}, see \figref{results/Push-TimePerContact-Location-Overall-Means}) %
and of \factor{Hand} (\anova{1}{1990}{16.1}, \pinf{0.001}, see \figref{results/Push-TimePerContact-Hand-Overall-Means})%
but not of the \factor{Positioning} \x \factor{Hand} interaction.
It was shorter with \level{Fingertips} than with \level{Wrist} (\percent{-15}, \pinf{0.001}), \level{Opposite} (\percent{-11}, \p{0.01}), or NoVi (\percent{-15}, \pinf{0.001});
and shorter with \level{Proximal} than with \level{Wrist} (\percent{-16}, \pinf{0.001}), \level{Opposite} (\percent{-12}, \p{0.005}), or \level{Nowhere} (\percent{-16}, \pinf{0.001}).
This showed different strategies to adjust the cube inside the target volume, with faster repeated pushes with the \level{Fingertips} and \level{Proximal} positionings.
It was also shorter with \level{None} than with \level{Skeleton} (\percent{-9}, \pinf{0.001}).
This indicates, as for the \chapref{visual_hand}, more confidence with a visual hand rendering.

\begin{subfigs}{push_results}{Results of the grasp task performance metrics.}[
    Geometric means with bootstrap \percent{95} \CI for each vibrotactile positioning (a, b and c) or visual hand rendering (d)
    and Tukey's \HSD pairwise comparisons: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
  ][
  \item Time to complete a trial.
  \item Number of contacts with the cube.
  \item Mean time spent on each contact.
  \item Mean time spent on each contact.
  ]
  \subfig[0.4]{results/Push-CompletionTime-Location-Overall-Means}
  \subfig[0.4]{results/Push-Contacts-Location-Overall-Means}
  \par
  \subfig[0.4]{results/Push-TimePerContact-Location-Overall-Means}
  \subfig[0.4]{results/Push-TimePerContact-Hand-Overall-Means}
\end{subfigs}