1 Learning User Clicks in Web Search Ding Zhou et al. The Pennsylvania State University IJCAI 2007

2 What is Click Prediction? microsoft xbox 360 kinect game

3 What is Click Prediction? microsoft xbox 360 kinect game 

4 Click Prediction Model P( | microsoft xbox 360 kinect game) P( | microsoft xbox 360 kinect game) P( | microsoft xbox 360 kinect game)

5 Two approaches 1. Full Model: P F ( TW/kinect | “ microsoft xbox 360 kinect game ” ) 2. Independent Model: P I ( | microsoft, xbox, 360, kinect, game)

6 Two Approaches: Pros and Cons Full Model High prediction accuracy Low coverage Independent Model Low prediction accuracy High coverage

7 New Approach: Conditional Probability Hierarchy P(url | microsoft xbox 360 kinect game) = P F (url | “ microsoft xbox 360 kinect game ” ) + (1- )P I (url | microsoft, xbox, 360, kinect, game)

8 New Approach: Conditional Probability Hierarchy P(url | microsoft xbox 360 kinect game) = P F (url | “ microsoft xbox 360 kinect game ” ) + (1- )P I (url | microsoft, xbox, 360, kinect, game) P I (url | microsoft, xbox, 360, kinect, game) = P(url|microsoft)P(url|xbox)P(url|360)P(url|kinect) P(url|game)

9 New Approach: Conditional Probability Hierarchy P(url | microsoft xbox 360 kinect game) = P F (url | “ microsoft xbox 360 kinect game ” ) + (1- )P I (url | microsoft, xbox, 360, kinect, game) P I (url | microsoft, xbox, 360, kinect, game) = P(url|microsoft)P(url|xbox)P(url|360)P(url|kinect) P(url|game)

10 New Approach: Conditional Probability Hierarchy microsoft xbox360kinect game P(url|microsoft xbox)P(url|360 kinect) P(url|360 kinect game) P(url|microsoft xbox 360 kinect game)

11 New Approach: Conditional Probability Hierarchy P(url | microsoft xbox 360 kinect game) = P F (url | “ microsoft xbox 360 kinect game ” ) + (1- )P I (url | microsoft, xbox, 360, kinect, game) P I (url | microsoft, xbox, 360, kinect, game) = f( P F (url | “ microsoft xbox ” ), (1- )P I (url | microsoft, xbox), P F (url | “ 360 kinect game ” ), (1- )P I (url | 360, kinect, game))

12 New Approach: Conditional Probability Hierarchy P(url | microsoft xbox 360 kinect game) = P F (url | “ microsoft xbox 360 kinect game ” ) + (1- )P I (url | microsoft, xbox, 360, kinect, game) is directly proportional to the occurrence frequency of “ microsoft xbox 360 kinect game ”

13 How to predict? What ’ s the threshold probability for considering P(url | microsoft xbox 360 kinect game) as a click???

14 How to predict? What ’ s the threshold probability for considering P(url | microsoft xbox 360 kinect game) as a click??? Not said in paper …

15 Experimental Corpus CiteSeer 1,826,817 query-click pairs

16 Prediction Accuracy

17 Prediction Coverage

18 Accuracy-Coverage Tradeoff