Understanding Society User Support

Dear UKHLS team,

I am trying to understand, based on Q11 and Q12 of the Weighting FAQ document, whether I can include the IEMB sample when pooling the data into financial years for cross-sectional analysis. Our population of interest are adults aged 18+ in England that have a common mental disorder (proxied by GHQ-12 score). I hope we can include the IEMB sample to help with numbers of observation when analysing by ethnicity.

I've pooled the data following Q12: months 4 to 15 from wave n, months 16 to 24 from wave n-1 and months 1-3 from wave n+1. Q12 says "data ... can be combined for cross-sectional analysis, provided that each of the 24 monthly samples is included in the analysis base an equal number of times". In the case of financial years, each has 12 sample months with IEMB (months 13 to 15 from wave n, and months 16 to 24 from wave n-1) and 12 sample months without IEMB (months 4 to 12 from wave n, and months 1 to 3 from wave n+1), so is equivalent to the original waves. My assumption was that (after adjusting the weights following the code on p10) I can use all subsamples including IEMB.

However in Q11, which is about calendar years or months, the advice is to exclude the IEMB because it is only part of months 13 to 24. For the BHPS and IEMB samples the advice is to use longitudinal weights to exclude them, but it seems one can use the Northern Ireland sample. Why is this, I don't understand the difference between these samples?

I also don't understand the example given for Northern Ireland weight adjustment: "please note that if you use months 13-24 you are excluding Northern Ireland from your analysis. If you use months 1-12 Northern Ireland will be over-represented without an additional adjustment to the weight. Here is the Stata syntax for adjustment if you use month 1-12: (...)." This sounds like using only sample months 1-12 (i.e. year 1) without months from year 2, which I thought I understood from Q12 shouldn't be done? Else, if it means using months 1-12 as part of a dataset pooling year 1 + year 2 sample months from different waves, then why do the Northern Ireland cases need extra adjustment? I seem to be missing something which might also help me understand if I can include the IEMB in my analysis sample.

Best wishes
Dorothee