LT-5 - 1 Chapter - 5 1 Category Medicine A Medicine B Male...

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Unformatted text preview: 1 Chapter - 5 1 Category Medicine A Medicine B Male 02/10 30/90 Female 48/90 10/10 Category Medicine A Medicine B Male 20.00 % 33.33 % Female 53.33 % 100.00 % Cure rate 50%.00 40.00% Medicines result 2 Which medicine is overall better? 2 Trees for numeric prediction 1. Regression: the process of computing an expression that predicts a numeric quantity 2. Regression tree: decision tree where each leaf predicts a numeric quantity 3. Predicted value is average value of training instances that reach the leaf 3 Constructing decision trees Strategy: top down 1. Recursive divide and conquer fashion 2. First: select attribute for root node 3. Create branch for each possible attribute value 4. Then: split instances into subsets 5. One for each branch extending from the node 6. Finally: repeat recursively for each branch, using only instances that reach the branch Stop if all instances have the same class 4 3 Problem Definition Acquisition of Background Knowledge Selection of Data Pre-processing of data Analysis and Interpretation Reporting and use Data Mining process 5 Credibility: Evaluating whats been learned Issues: training, testing, tuning Predicting performance Confidence Limit Holdout, cross-validation, bootstrap, leave- one-out Cost-sensitive measures Costs assigned to different types of errors Many practical applications involve costs The Minimum Description Length principle 6 4 Training and testing I Natural performance measure for classification problems: error rate Success: instances class is predicted correctly Error: instances class is predicted incorrectly Error rate: proportion of errors made over the whole set of instances How predictive is the model we learned? Error on the training data is not a good indicator of performance on future data 7 Training and testing II Test set: independent instances that have played no part in formation of classifier Assumption: both training data and test data are...
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LT-5 - 1 Chapter - 5 1 Category Medicine A Medicine B Male...

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