ClearAll[Modifier, CreateRandomNumber]
Modifier[x_] := If[x < 0.5, 2 (0.5 - x), 2 (x - 0.5)]
CreateRandomNumber[] := Module[{r1, r2, done = True},
  While[done,
   r1 = RandomReal[];
   r2 = RandomReal[];
   If[r2 < Modifier[r1],
    Return[r1];
    done = False
    ]
   ]
  ]
numbers = Table[CreateRandomNumber[], 100000];
{bins, counts} = HistogramList[numbers, {0, 1, 0.05}, "PDF"];
Grid[MapThread[{#1, " - ", StringJoin@ConstantArray["X", Round[20 #2]]} &, {Partition[bins, 2, 1], counts}], Alignment -> Left]