Why to restrict to TikZ-tree
or forest
? A simple matrix
also solves the problem:
\documentclass[tikz,border=2mm]{standalone}
\usetikzlibrary{positioning, matrix}
\begin{document}
\begin{tikzpicture}
\matrix[matrix of nodes, nodes={align=center, text width=2.4cm},
column sep=5mm, row sep=2mm] (A) {
&&&{Group 1\\ 300 Subjects}&{Treatment 1\\ Drug X 325 mg}& \\
&{600\\ Men}&{Random\\ Assignment} & & & Compare Drop in Temperature\\
&&&{Group 2\\ 300 Subjects}&{Treatment 2\\ Placebo}& \\
{1200\\ Subjects} & & & & &\\
&&&{Group 1\\ 300 Subjects}&{Treatment 1\\ Drug X 325 mg}& \\
&{600\\ Women}&{Random\\ Assignment} & & & Compare Drop in Temperature\\
&&&{Group 2\\ 300 Subjects}&{Treatment 2\\ Placebo}& \\
};
\draw[->] (A-4-1)--(A-2-2);
\draw[->] (A-2-2)--(A-2-3);
\draw[->] (A-2-3)--(A-1-4);
\draw[->] (A-1-4)--(A-1-5);
\draw[->] (A-1-5)--(A-2-6);
\draw[->] (A-2-3)--(A-3-4);
\draw[->] (A-3-4)--(A-3-5);
\draw[->] (A-3-5)--(A-2-6);
\draw[->] (A-4-1)--(A-6-2);
\draw[->] (A-6-2)--(A-6-3);
\draw[->] (A-6-3)--(A-5-4);
\draw[->] (A-5-4)--(A-5-5);
\draw[->] (A-5-5)--(A-6-6);
\draw[->] (A-6-3)--(A-7-4);
\draw[->] (A-7-4)--(A-7-5);
\draw[->] (A-7-5)--(A-6-6);
\node[draw, below right=of A.south west, anchor=north west, inner xsep=3mm] (B) {Assignment to block is not random};
\draw[<-] (A-4-1)--(A-4-1|-B.north);
\end{tikzpicture}
\end{document}

Update:
Just to show that forest
is probably better for schemes more similar to trees. I'm not a forest
expert, so it's not perfect: lower Placebo
nodes are not equally aligned. I hope someone could help.
\documentclass{standalone}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{forest}
\begin{document}
\begin{forest}
[1200\\ Subjects, for tree={align=center, grow'=east}
[600\\ Men
[{Random\\ Assignment}
[{Group 1\\ 300 Subjects}
[{Treatment 1\\ Drug X 325 mg}
[,phantom]
[,phantom]
[Compare Drop\\ in Temperature, name=aux11]
]
]
[{Group 2\\ 300 Subjects}
[{Treatment 2\\ Placebo}, name=aux12
]
]
]
]
[{600\\ Women}
[{Random\\ Assignment}
[{Group 1\\ 300 Subjects}
[{Treatment 1\\ Drug X 325 mg}
[,phantom]
[,phantom]
[Compare Drop\\ in Temperature, name=aux21]
]
]
[{Group 2\\ 300 Subjects}
[{Treatment 2\\ Placebo}, name=aux22
]
]
]
]
]
\draw (aux11)--(aux12) (aux21)--(aux22);
\end{forest}
\end{document}

forest
is based on TikZ, so it is indeed not very different.forest
input syntax is simple and it can do many things programmatically, which in the base methods are I'm sure possible, but by no means trivial.forest
. :)istgame
thing is easier for game-theory trees, though obviously less flexible. And the tree layout algorithms of TikZ might be nice, if your trees require that level of automation. Otherwise, if it is a tree in the graph-theory sense, Forest; otherwise TikZ.