1. Life Opportunities Survey (LOS) Wave 2 Weighting Andy Fallows and Sangeetha Gallagher

2. Overview Background Design W1 Weighting Longitudinal W2 Weighting Issues with weighting

3. Background Commissioned by DWP Follows social model of disability Longitudinal survey of population (possible boosts) Comparison of how people participate in society

4. Design Cross-sectional survey at W1 People identified as impaired at W1 interviewed face to face at W2 Sub-sample of non-impaired interviewed face to face at W2, remainder given telephone interview If telephone interview identifies respondent as having gained an impairment then get face to face interview

5. Design W1 Selected Sample

6. Design W1 Respondents W1 Non- Respondents

7. Design Non-Impaired Impaired

8. Design Non-Impaired Impaired Comparison Screening

9. Design Non-Impaired Impaired Comparison Screening

10. Design Non-Impaired Impaired Comparison Screening Onset

11. Design (Complex) Non-Impaired Impaired Comparison Screening Onset (Telephone) Onset (F2F) Offset

12. Design (Super Complex) Non-Impaired Impaired Comparison Screening Onset (Telephone) Onset (F2F) Offset Household of Comparison Household of Impaired Household of Onset (Telephone)

13. Design (Summary) Face to Face Telephone

14. W1 Weighting Follows standard social survey weighting Design weight calculated as inverse of probability of selection (taking account of multi-household adjustment) Non-response weight based on Output Area Classification

15. W1 Weighting Weights calibrated to Age-Sex and Region totals Totals obtained from ONS Demography – Census totals carried forward Calibration ensures that weights sum to population totals 15

16. Longitudinal (W2) Weighting Start with W1 final weight Create attrition weight by modelling unknown eligibility and response propensities using W1 variables and logistic regression Scale weights to make sure correct proportions of ineligibles are observed Calibrate back to W1 totals

17. Weight for everyone in survey Weight-1 Carry over the Wave 1 calibration weight as base weight Adjust for attrition Calibrate to Wave 1 population total But...... Number of questions asked are different

18. Why the difference Telephone interviewFace to face interview Screening households Impaired person households Control households Onset person household How can you compare between Wave 1 and Wave 2 if some questions are not asked in Wave 2?

19. Solution 1 PopulationSample Impaired Impaired including onsets Not Impaired Control Screening PopulationSample Impaired Impaired including onsets Not ImpairedControl Keep Weight 1 Reweighted

20. Weighting the not impaired Design weight = 1/P (ctrl-hhld) Adjust for attrition Calibrate to size of wave 1 population of not impaired people = w1 population – sum(weight of w2 impaired)

21. Design weight for control group ABC selected Not selected selected Not selected selected Not selected P (ctrl-hhld) = 1 – P (not selected)

22. Solution 1 or Weight 2 Weight 2 = design weight*attrition weight*g weight Weight 2 = Weight 1 Estimates not conforming to wave1 More exploratory work on why estimates are lower than expected Not Impaired at wave 2 Impaired at wave 2

23. Findings Control group Telephone interview (Screening group) OnsetNot onset Face to face interview OnsetABC Not Onset DEF TotalA + DB + EC + F B/(B+E) is biased A/(A+D) is unbiased C/(C+F) is unobserved

24. Solution 2 – Weight 3 Give weight to people who had only a face to face interview Split the people who were interviewed face to face in Wave 2 but were not impaired in Wave 1 into weighting classes People who were identified as in onset household through telephone interview shared the weight of those who were in the same weighting class and had only face to face interview

25. Variables forming weighting classes 25

26. Continued.... 26

27. Weight 3

28. Final weight People who were identified as impaired in Wave 1 were weighted as People who had a face to face interview in Wave 2 but were not impaired in Wave 1 were weighted as

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