diff --git a/06-Multivariate-Kalman-Filters.ipynb b/06-Multivariate-Kalman-Filters.ipynb
index 954f94a..962e409 100644
--- a/06-Multivariate-Kalman-Filters.ipynb
+++ b/06-Multivariate-Kalman-Filters.ipynb
@@ -1909,7 +1909,7 @@
     "In the univariate chapter we scaled the mean using this equation\n",
     "\n",
     "$$\n",
-    "\\mu =\\frac{\\bar\\sigma^2 \\mu_2 + \\sigma_\\mathtt{z}^2 \\bar\\mu} {\\bar\\sigma^2 + \\sigma_\\mathtt{z}^2}$$\n",
+    "\\mu =\\frac{\\bar\\sigma^2 \\mu_z + \\sigma_\\mathtt{z}^2 \\bar\\mu} {\\bar\\sigma^2 + \\sigma_\\mathtt{z}^2}$$\n",
     "\n",
     "which we simplified to\n",
     "\n",