1. Respondent Driven Sampling (RDS) Keith Chan BC CfE

3. RDS of drug users in Recife, Brazil IDU DU

4. www.respondentdrivensampling.org www.respondentdrivensampling.org Douglas Heckathorn, Cornell

5. Obstacles Hard to reach populations Lack of sampling frame Convenience sample Biased estimates Not generalizable

6. RDS hopes Valid identification of population members Population-based estimates Efficient recruitment of hidden populations

7. RDS issues Many assumptions and requirements Many potential biases may not disappear Difficulties in analysis of RDS data Success and failures of RDS worldwide

8. RDS Assumptions 1.Recruits who’s network is members of the target population 2.Network forms one single large component 3.Report network size accurately 4.Recruit randomly from network 5.Sampling with replacement

9. RDS Necessary Data Requirements 1.Personal Network Size 2.Respondent's Serial Number - Serial number of the coupon the respondent was recruited with 3.Respondent's Recruiting Serial Numbers - Serial numbers from the coupons the respondent is given to recruit others

11. Important Coupon Information

12. RDS of drug users in Recife, Brazil IDU Non IDU

13. RDS study of MSM, Kampala, Uganda

14. Markov Process Assumption Memoryless As the recruitment process continues from wave to wave, an equilibrium mix of recruits will eventually be attained This equilibrium mix is independent of the characteristics of the subject from which the recruitment began

15. Equilibrium of education, MSM, Uganda Did not complete high school Completed high school

16. No foreign sex partner Had any foreign sex partner Equilibrium of sex with foreigners, MSM, Uganda

18. Network Size Question Meant to assess the size of the network from which a person could actually recruit within a reasonable time 1.How many other ____ do you know and you will see in the next month? 2.How many other ____ do you know and you will see in the next week?

19. Reciprocal Relationship Assumption

25. Analysis Sample size calculation Crude vs. adjusted Univariate Bivariate Weights Multivariate Netdraw Aggregate analyses Statistical tests Design effect adjustment

31. RDS of drug users in Recife, Brazil IDU seed Never grew. Requested from Brazilia permission to change to all drug users.

32. RDS of drug users in Recife, Brazil IDU DU

33. IDU: Failures Russia Kosovo

34. IDU: Successes USA Indonesia India VietnamMexico Estonia Russia Thailand Nepal MontenegroSerbia Iran

35. Female sex workers: Failures Serbia, Montenegro, Albania, Russia Caribbean Paraguay

36. Female sex workers: Successes Honduras Papua New Guinea India Vietnam

37. MSM: Failures Kosovo Caribbean Albania Estonia Cambodia

38. MSM: Successes Honduras Papua New Guinea Bangladesh Zanzibar Thailand Nepal Croatia Egypt Uganda USA Iran South Africa Brazil