diff --git a/materials/worksheet_09/worksheet_09.ipynb b/materials/worksheet_09/worksheet_09.ipynb
index cfa9018..6f9e066 100644
--- a/materials/worksheet_09/worksheet_09.ipynb
+++ b/materials/worksheet_09/worksheet_09.ipynb
@@ -222,7 +222,7 @@
     "editable": false,
     "nbgrader": {
      "cell_type": "code",
-     "checksum": "36ff1c22b8a2cc1ab0292fa7f9de8672",
+     "checksum": "f31c591df842e20e75b667f8f56baf3d",
      "grade": false,
      "grade_id": "cell-3363ef5dcb1be0f5",
      "locked": true,
@@ -239,7 +239,6 @@
    "source": [
     "options(repr.plot.width=8, repr.plot.height=6)\n",
     "library(broom)\n",
-    "install.packages(\"latex2exp\")\n",
     "library(latex2exp)\n",
     "library(tidyverse)\n",
     "library(tidymodels)\n",
@@ -2702,7 +2701,7 @@
     "editable": false,
     "nbgrader": {
      "cell_type": "markdown",
-     "checksum": "f40b8cc5bbc3266d66abc8fe691b5576",
+     "checksum": "26c24a118caba2567a94159b1a1d7484",
      "grade": false,
      "grade_id": "cell-e6c3ceb269ad8bd1",
      "locked": true,
@@ -2715,7 +2714,7 @@
     "**Question 4.0**\n",
     "<br>{points: 1}\n",
     "\n",
-    "Use the function `rmse()` to compute the $\\text{RMSE}_{\\text{test}}$ of the new predictive model `Housing_test_pred_red_OLS` using the test set `testing_Housing`. Add this metric as another row in the tibble `Housing_R_MSE_models` with `\"OLS Reduced Regression\"` in the column `Model` and the corresponding $\\text{RMSE}_{\\text{test}}$ in column `R_MSE`.\n",
+    "Use the new reduced predictive model, `Housing_red_OLS`, to predict the response in the test set `testing_subset`. Use the resulting predictive values to compute the error and the $\\text{RMSE}_{\\text{test}}$ of the predictive values. Add this metric as another row in the tibble `Housing_RMSE_models`. Identify the new row as `\"OLS Reduced Regression\"` (in column `Model`) and enter the corresponding $\\text{RMSE}_{\\text{test}}$ in the column `RMSE`.\n",
     "\n",
     "> Note: since you are adding a row to an existing object, you may need to restart the kernel or rerun the cell with the original data frame to avoid extra concatenation.\n",
     "\n",