\documentclass[a4paper]{article}

\usepackage{pgfplots}

\usepgfplotslibrary{statistics}

\begin{document}
\def\TEST#1{%
	\begin{tikzpicture}
	%\tracingmacros=2 \tracingcommands=2
		\begin{axis}[
		]
		\addplot+[
			boxplot prepared={
				lower whisker=5,
				lower quartile=7,
				median=8.5,
				upper quartile=9.5,
				upper whisker=10,
				#1,
			},
		]
		table[row sep=\\,y=v] {
		v\\
		%1\\	3\\	5\\	6\\	7\\	7\\	7\\	8\\	8\\	8\\	9\\	9\\	9\\	9\\	9\\	10\\	10\\	10\\	10\\	10\\
		1\\	3\\%	5\\	6\\	7\\	7\\	7\\	8\\	8\\	8\\	9\\	9\\	9\\	9\\	9\\	10\\	10\\	10\\	10\\	10\\
		};

		\end{axis}
	\end{tikzpicture}
	\message{END.}%
}%

\TEST{}

\TEST{draw relative anchor=1}


\TEST{draw relative anchor=0}
\end{document}

