Tiantian's methodology and next week plan

(Tiantian's methodology and next week plan) README.md

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+# Methodology
+Upload your methodology description here
+
+How should we deal with the strongly right skewed data?
+- After discussion with professor we decided to delete all the cases with grade of zero, and cases with unreasonably extreme data 
+- Then we will change our research aim to find what and how features are correlated with students’ grades for online courses given they finished assignments.
+      - We have two options of methodology. We decided to compare two methodologies.
+        - Method 1: More traditional regression model with cross validation. Base on our visualization, the regression would be linear. 
+            - Assumption for linear regression:
+                  - Linear relationship
+                  - Multivariate normality
+                  - No or little multicollinearity
+                  - No auto-correlation
+                  - Homoscedasticity
+        - Method 2:  Classification And Regression Tree (CART) analysis
+         -Assumption: there's no distributional assumption for data.
+- Validation
+      - we'll use cross validation techinique.We'll generate a model for one class. And then we'll apply it to other classes and see whether it can also fit well. 
+
+Next week:
+ Clean the data, do the deletion 
+ Study how to use R to produce Scatter Plots and Correlation Matrix
+