Fix Error in A Primer on Bayesian Methods for Multilevel Modeling (#562)

* Rename floor_ind to floor_idx

* Switch from `floor_idx` to `floor_ind`

* Switch from `floor_idx` to `floor_ind` in ipynb

Author: henrytdsimmons

examples/case_studies/multilevel_modeling.ipynb

@@ -688,7 +688,7 @@
     "coords = {\"county\": mn_counties}\n",
     "\n",
     "with pm.Model(coords=coords) as unpooled_model:\n",
-    "    floor_idx = pm.MutableData(\"floor_ind\", floor_measure, dims=\"obs_id\")\n",
+    "    floor_ind = pm.MutableData(\"floor_ind\", floor_measure, dims=\"obs_id\")\n",
     "\n",
     "    alpha = pm.Normal(\"alpha\", 0, sigma=10, dims=\"county\")\n",
     "    beta = pm.Normal(\"beta\", 0, sigma=10)\n",

examples/case_studies/multilevel_modeling.myst.md

@@ -242,7 +242,7 @@ Let's now turn our attention to the unpooled model, and see how it fares in comp
 coords = {"county": mn_counties}
 
 with pm.Model(coords=coords) as unpooled_model:
-    floor_idx = pm.MutableData("floor_ind", floor_measure, dims="obs_id")
+    floor_ind = pm.MutableData("floor_ind", floor_measure, dims="obs_id")
 
     alpha = pm.Normal("alpha", 0, sigma=10, dims="county")
     beta = pm.Normal("beta", 0, sigma=10)