challenge and extra reading

TimeSeries/2-ARIMA/README.md

@@ -347,11 +347,11 @@ plt.show()
 A very nice plot, showing a model with good accuracy. Well done!
 ## 🚀Challenge
 
-TBD
+Dig into the ways to test the accuracy of a Time Series Model. We touch on MAPE in this lesson, but are there other methods you could use? Research them and annotate them. A helpful document can be found [here](https://otexts.com/fpp2/accuracy.html)
-## [Post-lecture quiz](link-to-quiz-app)
 
+## [Post-lecture quiz](link-to-quiz-app)
 ## Review & Self Study
 
-TBD
+This lesson touches on only the basics of Time Series Forecasting with ARIMA. Take some time to deepen your knowledge by digging into [this repository](https://microsoft.github.io/forecasting/) and its various model types to learn other ways to build Time Series models.
 
-**Assignment**: [Assignment Name](assignment.md)
+**Assignment**: [A new ARIMA model](assignment.md)

TimeSeries/2-ARIMA/assignment.md

@@ -1,9 +1,10 @@
-# [Assignment Name]
+# A new ARIMA model
 
 ## Instructions
 
+Now that you have built an ARIMA model, build a new one with fresh data (try one of [these datasets from Duke](http://www2.stat.duke.edu/~mw/ts_data_sets.html). Annotate your work in a notebook, visualize the data and your model, and test its accuracy using MAPE.
 ## Rubric
 
-| Criteria | Exemplary | Adequate | Needs Improvement |
+| Criteria | Exemplary                                                                                                           | Adequate                                                 | Needs Improvement                   |
-| -------- | --------- | -------- | ----------------- |
+| -------- | ------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------- | ----------------------------------- |
-|          |           |          |                   |
+|          | A notebook is presented with a new ARIMA model built, tested and explained with visualizations and accuracy stated. | The notebook presented is not annotated or contains bugs | An incomplete notebook is presented |