1. When can the instance based learning be used? Give an example that the instance based learning is suitable. 2. What is the main challenge of KNN method? What kind of methods can be used to face the challenge? 3. List out 4 distance functions. 4. In the space shuttle O-ring data set in following table the target variable, the Number of O-rings with Stress, has three values: 0, 1, and 2. Consider these three values as categorical values, instances # 13-23 as the training data, instances # 1-12 as the testing data, and the Euclidean distance as the measure of dissimilarity. Construct a l-nearest neighbor classifier and a 3-nearest neighbor classifier, and test and compare their classification performance. Target variable Number of O rings with Stress 0 1 1 2 3 0 0 4 5 6 7 8 9 10 11 12 13 14 15 16 Attribute variables number of O- Launch rings temperature 6 66 6 70 6 69 6 68 6 67 6 72 6 73 6 70 6 57 6 63 6 70 6 78 6 67 6 53 6 67 6 75 6 70 6 81 6 76 6 79 6 75 6 76 6 58 Leak-Check Pressure 50 50 50 50 50 50 100 100 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 0 0 0 0 1 1 1 0 0 2 0 0 0 17 0 0 0 18 19 20 21 22 23 0 0 1 5. How to decide k in K Nearest Neighbor