Fix math display

exercises/jsp.md

@@ -1,13 +1,4 @@
----
-title: "Exercise: Junior School Project"
-author: "Nora Wickelmaier"
-output:
-  md_document:
-    variant: gfm
-    preserve_yaml: true
-kramdown:
-  math_engine: mathjax
----
+# Exercise: Junior School Project
 
 Load the Junior School Project collected from primary (U.S. term is
 elementary) schools in inner London in R. You might need to install the
@@ -117,8 +108,8 @@ aggregate(gcraven ~ school, dat, mean) |> head()
     $$
 
     with
-    $$\boldsymbol\upsilon \sim N(\boldsymbol 0, \boldsymbol{\Sigma}_\upsilon)$$
-    i.i.d., $$\varepsilon_{ij} \sim N(0, \sigma^2)$$ i.i.d.
+    $\boldsymbol\upsilon \sim N(\boldsymbol 0, \boldsymbol{\Sigma}_\upsilon)$
+    i.i.d., $\varepsilon_{ij} \sim N(0, \sigma^2)$ i.i.d.
 
 5.  Interpret the parameters of the model: