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. – user121799 Aug 8 '18 at 23:45forest
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. – Alan Munn Aug 8 '18 at 23:51forest
. :) – Alan Munn Aug 8 '18 at 23:55istgame
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. – cfr Aug 9 '18 at 2:02