1. Free Powerpoint Templates Page 1 Free Powerpoint Templates Influence and Correlation in Social Networks Azad University KurdistanSocial Network

2. Free Powerpoint Templates Page 2 Proffessor: Dr shaykh Esmaili Presenters: Alireza Zandi Asrin Mohammadi Somaye Yosefi Social Network Influence and Correlation in Social Networks Azad University Kurdistan

3. Free Powerpoint Templates Page 3 Outline Social Network Introduction Models of social correlation Methodology Simulations Experiments on real data Influence and Correlation in Social Networks Azad University Kurdistan

4. Free Powerpoint Templates Page 4 Social systems Online social networks: are playing an ever- important role in shaping the behavior of users on the web. – Network of professional contacts (e.g., for finding jobs) –Network of colleagues (e.g., for learning new techniques) –Web 2.0 systems: Online social networks: facebook, myspace, orkut, IM, linkedIn, twitter, … Content sharing: flickr, del.icio.us, youtube, weblogs, … Content creation: wikipedia Social Network Influence and Correlation in Social Networks Azad University Kurdistan

5. Free Powerpoint Templates Page 5 Social correlation There has been some theoretical and empirical work on how a user's actions can be correlated to his/her social affliations. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

6. Free Powerpoint Templates Page 6 correlation in social networks Causes of correlation in social networks can be categorized into roughly three types. – The first is influence,where the action of a user is triggered by one of his/her friend's recent actions. – The second is homophily,which means that individuals often befriend others who are similar to them. – The third is environment (also known as confounding factors or external influence). Social Network Influence and Correlation in Social Networks Azad University Kurdistan

7. Free Powerpoint Templates Page 7 Social influence Given the signficance of social influence. – This is a particularly difficult problem in online settings. – We overcome this problem by taking advantage of the availability of data about the timing of actions in online settings. –We propose a statistical test (called the shuffle test). – We also show the efectiveness of our test using simula- tions. Our test cases are based on a large social network from Flickr. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

8. Free Powerpoint Templates Page 8 Models of social correlation We study a setting where a group of individuals (also called agents or users) are nodes of a social network G. – G is generated from an unknown probability distribution this means that for two nodes u and v that are adjacent in G, the events that u becomes active is correlated with v becoming active.. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

9. Free Powerpoint Templates Page 9 Models of social correlation Social correlation –Is correlation between the behavior of aliated agents in a social network is a well-known phenomenon. There are three primary explanations for this phenomenon: – homophily, the environment, and social inuence. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

10. Free Powerpoint Templates Page 10 Models of social correlation Homophily – Homophily is the tendency of individuals tochoose friends with similar characteristics Confounding –The second explanation for correlation between actions of adjacent agents in a social network is external inuence from elements in the environment. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

11. Free Powerpoint Templates Page 11 Models of social correlation Influence –The third, and perhaps the most consequential explanation for social correlation is social inuence. This refers to the phenomenon that the action of individuals can induce their friends to act in a similar way. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

12. Free Powerpoint Templates Page 12 Example: obesity study Data set of 12,067 people from 1971 to 2003 as part of Framingham Heart Study Social Network Influence and Correlation in Social Networks Azad University Kurdistan

13. Free Powerpoint Templates Page 13 Example: obesity study Results –Having an obese friend increases chance of obesity by 57%. –obese sibling ! 40%, obese spouse ! 37% Social Network Influence and Correlation in Social Networks Azad University Kurdistan

14. Free Powerpoint Templates Page 14 Models of social influence Many models proposed in different settings –Game-theoretic models Each agent modeled as a player in a “game”. The utility that an agent derives depends on what his/her friends do. Agents decide whether to become active to maximize their utility. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

15. Free Powerpoint Templates Page 15 Models of social influence -Probabilistic models Probabilistic models are more predictive –allows optimization (find the best “seed set”) –allows fitting the data to estimate parameters of the system Social Network Influence and Correlation in Social Networks Azad University Kurdistan

16. Free Powerpoint Templates Page 16 Models of social influence Influence Model Graph (static or dynamic) Edge (u,v): Node u can influence node v Discrete time: t = 0, 1, 2, … For each t, every inactive node becomes active with Social Network Influence and Correlation in Social Networks Azad University Kurdistan

17. Free Powerpoint Templates Page 17 Models of social influence probability p(x), where x is the active contacts Social Network

18. Free Powerpoint Templates Page 18 Model Influence model: each agent becomes active in each time step independently with probability p(a), where a is the of active friends. Natural choice for p(a): logistic regression function: with ln(a+1) as the explanatory variable. I.e., Coefficient α measures social correlation. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

19. Free Powerpoint Templates Page 19 Measuring social correlation We compute the maximum likelihood estimate for parameters α and β. Let Y a = pairs (user u, time t) where u is not active and has a active friends at the beginning of time step t, and becomes active in this step. Let N a = …… does not become active in this step. Find α, β to maximize Social Network Influence and Correlation in Social Networks Azad University Kurdistan

20. Free Powerpoint Templates Page 20 Social Network Influence and Correlation in Social Networks Azad University Kurdistan Sample

21. Free Powerpoint Templates Page 21 Social Network Influence and Correlation in Social Networks Azad University Kurdistan Sample

22. Free Powerpoint Templates Page 22 Social Network Influence and Correlation in Social Networks Azad University Kurdistan Sample

23. Free Powerpoint Templates Page 23 Test Shuffle Edge-Reversal Social Network Influence and Correlation in Social Networks Azad University Kurdistan

24. Free Powerpoint Templates Page 24 simulations Generative models Measuring correlation Distinguishing influence Social Network Influence and Correlation in Social Networks Azad University Kurdistan

25. Free Powerpoint Templates Page 25 no-correlation model: actions generated randomly to follow the pattern of one of the real tags, but ignoring network Influence model: same as described, with a variety of (α,β) values Correlation model(no-influence): pick a # of random centers, let W be the union of balls of radius 2 around these centers Social Network Influence and Correlation in Social Networks Azad University Kurdistan Generative models

26. Free Powerpoint Templates Page 26 Simulation results, baseline Social Network Influence and Correlation in Social Networks Azad University Kurdistan

27. Free Powerpoint Templates Page 27 Distribution of for the influence model Social Network Influence and Correlation in Social Networks Azad University Kurdistan

28. Free Powerpoint Templates Page 28 Distribution of for the correlation model Social Network Influence and Correlation in Social Networks Azad University Kurdistan

29. Free Powerpoint Templates Page 29 Shuffle test, influence model Social Network Influence and Correlation in Social Networks Azad University Kurdistan

30. Free Powerpoint Templates Page 30 Shuffle test, correlation model Social Network Influence and Correlation in Social Networks Azad University Kurdistan

31. Free Powerpoint Templates Page 31 Edge-reversal test, influence mode l Social Network Influence and Correlation in Social Networks Azad University Kurdistan

32. Free Powerpoint Templates Page 32 Edge-reversal test, correlation model Social Network Influence and Correlation in Social Networks Azad University Kurdistan

33. Free Powerpoint Templates Page 33 Experiments on real data The Flickr dataset Measuring correlation Distinguishing influence Social Network Influence and Correlation in Social Networks Azad University Kurdistan

34. Free Powerpoint Templates Page 34 Flickr tags ~10K tags We focus on a set of 1700 Different growth patterns: –bursty (“halloween” or “katrina”) –smooth (“landscape” or “bw”) –periodic (“moon”) For each tag, define an action corresponding to using the tag for the first time. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

35. Free Powerpoint Templates Page 35 Distribution of for the Flickr social network. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

36. Free Powerpoint Templates Page 36 Shuffle test on Flickr data Social Network Influence and Correlation in Social Networks Azad University Kurdistan

37. Free Powerpoint Templates Page 37 Edge-reversal test on Flickr data Social Network Influence and Correlation in Social Networks Azad University Kurdistan

38. Free Powerpoint Templates Page 38 Conclusions Our contributions –Defined two models that exhibit correlation, one with and the other without social influence. –Developed statistical tests to distinguish the two –Theoretical justification for one of the tests. –Simulations suggest that the tests “work” in practice. –On Flickr, we conclude that despite considerable correlation, no social influence can be detected. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

39. Free Powerpoint Templates Page 39 Conclusions Discussion –cannot conclusively say there is influence without controlled experiments (example: flu shot) –still can rule out potential candidates –Open: develop algorithms to find “influential” nodes/communities given a pattern of spread. Social Network Influence and Correlation in Social Networks Azad University Kurdistan

40. Free Powerpoint Templates Page 40 ?