Data Quality of the NHIS and the Contact History Instrument

1. Data Quality of the NHIS and theContact History Instrument Barbara Stussman Catherine Simile Division of Health Interview Statistics National Center for Health Statistics Centers for Disease Control and Prevention Data Users Conference July 10, 2006

2. The findings and conclusions in this presentation are those of the author(s) and do not necessarily represent the views of the Centers for Disease Control and Prevention.

3. Purpose Describe how the implementation of CHI—the Contact History Instrument—is being used to improve the data quality of the National Health Interview Survey

4. Overview • Non-Response: Why do we care? • Description of CHI • Research Examples • Future Directions

5. Non Response: Why do we Care?

6. Example Sample Composition Participating Non- Sample Responders

7. Bias • Nonresponse is a problem to the extent that it biases estimates • Two components to bias: • proportion of non-responders • difference between non-responders and responders on variables of interest

8. Diabetes Example:Response Rate Low, No Difference, No bias 50% Responders, Prevalence = 10% 50% Non-responders, Prevalence = 10% True Estimate = (.50)(.10) + (.50)(.10) = 10% Responding Sample Estimate = 10% No bias, regardless of the high non-response rate

9. Diabetes Example:Response Rate High, Difference large, A little bias 97% Responders, Prevalence = 10% 3% Non-responders, Prevalence = 30% True Estimate = (.97)(.10) + (.03)(.30) = 10.6% Responding Sample Estimate = 10.0% Because the response rate is high, even though the difference in prevalence is high, the bias is small

11. Two Approaches to Combating Non-Response • Interventions to reduce it • Knowing and living with its impact

12. Description of CHI

13. CHI Background • 2002 Inter-Agency Nonresponse Summit • Developed by the Census Bureau for surveys using Census as data collection agency • Part of 2004 NHIS Redesign

14. Contact History Instrument • Allows interviewers to record information on every attempt to make contact with a household • (whether successful or not) • Interviewer enters information into laptop as close to time of attempt as possible • Unique opportunity to learn about every interaction between interviewer and household

21. Summary: CHI Instrument • Data on approximately 200,000 Visit attempts • Collects information per attempt on: • Mode of contact attempt • Contact or noncontact • Outcome of attempt (complete, partial, unable to conduct interview) • Concerns/Reluctance • Strategies attempted

22. Examples of CHI Research

23. Research Topics • Optimal Call Times • Interviewer Strategies

24. Optimal Call Times • What is the optimal time for making a contact attempt? • When are interviewers making attempts? • Does time of first contact influence outcome? • Are interviewers making attempts at optimal times?

26. More Results: Optimal Times • More first attempts occur on weekday afternoons; shift to weekends and evenings on second and later attempts • Weekday evenings and weekends best time for making first contact • Weekday afternoon first contacts more likely to result in complete interview than weekday evening first contacts

27. Interviewers Strategies • What strategies are interviewers using and in what combination? • In what ways do interviewers shift strategies with different field situations? • How is the use of certain strategies related to gaining contact and/or cooperation?

28. Strategies Used on 1st, 2nd, 3rd Attempts

29. Number of Strategies Used per Attempt

30. Knowing and Living with the Impact of Non-Response

31. Sample Composition More Willing High Non- Responders Effort Respon- Respon- ders ders ___________________________________

32. Defining High Effort Responders Definition 1: Cooperation Field Representative indicated at least one time in the contact history of the case that the case could be a potential refusal. Definition 2: Contactability Field Representative attempted to contact a household at least 4 times before making contact with a member of the household.

33. Sample Health Indicators • Reported Diagnosed Conditions • Diabetes • Hypertension • Arthritis

34. How different are High Effort Responders from Lower Effort Responders on Selected Health Indicators?

35. Diagnosed Conditions

36. To what degree are the national health estimates biased?

37. Estimating Diagnosed Conditions

38. Bias summary • There are significant and substantive differences between high and low effort groups • Though there is a small effect on the national estimates, should the proportion of the high effort grow, we would expect a greater impact • These estimates are at the national level and do not speak to subgroup analyses

39. Future Directions • CHI has been a valuable tool for learning about data quality • Our goal is to use this research to make specific field recommendations we hope will lead to an increase in response rates • Use it to continue to produce high quality health estimates

40. Contact Information Barbara Stussman Catherine M. Simile National Center for Health Statistics Division of Health Interview Statistics 3311 Toledo Road, Room 2115 Hyattsville, MD 20782 Barbara, (301) 458-4529 Catherine, (301) 458-4499 Email: bstussman@cdc.gov; csimile@cdc.gov