documentclass[12pt,oneside,a4paper,fleqn]{report}


 usepackage{forest}
 usepackage{tikz}
 tikzset{
    dot/.style={circle,draw,inner sep=1.5,fill=black},
   }

  begin{document}




 begin{forest}
    [ ,name=a,for tree={s sep=50pt,l sep=5cm,dot,grow=1},
    [ ,name=b,edge label={node[midway, yshift=0.3cm,font=small]{$p^2_1        =0.6,~ d_1^2=4$}}
      [ ,name=c,edge label={node[midway, yshift=0.3cm,font=small]{$p^3_4 =0.25,~ d_4^3=5$}}  ]
  [,name=d, edge label={node[midway, yshift=0.3cm,font=small]{$p^3_3    =0.25,~ d_3^3=2$}}  ]
  ]
    [ ,name=e, edge label={node[midway, yshift=0.3cm,font=small]{$p^2_1 =0.4,~ d_1^2=1.5$}}
    [,name=g,edge label={node[midway, yshift=0.3cm,font=small]{$p^2_1 =0.3,~ d_2^3=5$}}  ]
      [,name=h,edge label={node[midway, yshift=0.3cm,font=small]{$p^2_1 =0.2,~ d_1^3=2$}}  ]
   ]
 ]
 node[yshift=-5cm,name= tiii,font=small] at (a) {$t=1$};
 node[name= tii,font=small] at (c|-tiii) {$t=3$};
 node[name= t,font=small] at (b|-tii) {$t=2$};
end{forest}


 end{document}