I am using stata to work with IPUMS NHIS data from 2002, 2009 and 2016. When I tried to get weighted odds ratios of my outcomes, I got estimates without confidence intervals and a message saying “missing standard errors because of stratum with single sampling unit.” I was able to find the 10 strata w singleton PSU’s. Given the sampling strategy, do you recommend combining the singleton PSU’s with the strata before or after, deleting them, or something else? I’ve read elsewhere that deciding what to do with singleton PSU’s depends on how the data is collected.

A second, separate question: If I am using data from the 3 years to compare certain outcomes between years, do I need to divide the sampling weight by 3 (as suggested in other posts)?

Thanks for your time.