diff --git a/HowBadIsMyBatch.ipynb b/HowBadIsMyBatch.ipynb
index 55e7506ceb6..3687098d3cd 100644
--- a/HowBadIsMyBatch.ipynb
+++ b/HowBadIsMyBatch.ipynb
@@ -100,14 +100,19 @@
     "        self.dataFrame = dataFrame        \n",
     "\n",
     "    def filterBy(self, manufacturer = None, dose = None):\n",
-    "        # FK-TODO: extract private instance methods\n",
-    "        isCovid19 = self.dataFrame[\"VAX_TYPE\"] == \"COVID19\"\n",
-    "        isManufacturer = self.dataFrame[\"VAX_MANU\"] == manufacturer if manufacturer is not None else True\n",
-    "        isDose = self.dataFrame[\"VAX_DOSE_SERIES\"].str.contains(dose) if dose is not None else True\n",
-    "        return self.dataFrame[isCovid19 & isManufacturer & isDose]\n",
+    "        return self.dataFrame[self._isCovid19() & self._isManufacturer(manufacturer) & self._isDose(dose)]\n",
     "\n",
     "    def filterForSevereEffects(self, dose):\n",
-    "        return self.filterBy(dose = dose)\n"
+    "        return self.filterBy(dose = dose)\n",
+    "\n",
+    "    def _isCovid19(self):\n",
+    "        return self.dataFrame[\"VAX_TYPE\"] == \"COVID19\"\n",
+    "\n",
+    "    def _isManufacturer(self, manufacturer):\n",
+    "        return self.dataFrame[\"VAX_MANU\"] == manufacturer if manufacturer is not None else True\n",
+    "\n",
+    "    def _isDose(self, dose):\n",
+    "        return self.dataFrame[\"VAX_DOSE_SERIES\"].str.contains(dose) if dose is not None else True\n"
    ]
   },
   {