replace tikz picture with png

15_hierarchical_modelling.ipynb

@@ -367,27 +367,8 @@
       "source": [
         "On the level of data, hierarchies usually are expressed in terms of groups:\n",
         "\n",
-        "```{tikz}\n",
-        "% Nodes\n",
-        "\\node (pop) {population}\n",
-        "    % Second level nodes\n",
-        "    child { node (group1) {group1}\n",
-        "      % Third level nodes for Group 1\n",
-        "      child {node {$y_{11}$} }\n",
-        "    }\n",
-        "    child { node (group2) {group2}\n",
-        "      % Third level nodes for Group 2\n",
-        "      child { node {$y_{21}$} }\n",
-        "      child { node {$y_{22}$} }\n",
-        "      % Add more children for Group 2 as needed\n",
-        "    };\n",
+        "![](assets/pop_group.png)\n",
         "\n",
-        "% Arrows\n",
-        "  \\draw[->] (pop) -- (group1);\n",
-        "  \\draw[->] (pop) -- (group2);\n",
-        "  \\draw[->] (pop) -- (group2);\n",
-        "  \\draw[->] (pop) -- (group2);\n",
-        "```\n",
         "\n",
         "For example, $y_{2j}$ here could represent repeated measurements within the same group."
       ]