The Stata versions we tried were 8, 9, 11 and 12 and SPSS version was 22. With regards to the query on whether to export the original missing values or as .a/.b, I feel it would be preferable to keep the original value.

Thanks and Regards

Dr. Divya Nair Assistant Professor | Dept. of Community Medicine Sri Venkateshwaraa Medical College Hospital & Research Centre Ariyur | Pondicherry 605 102. Mob: 8056748342 | Alternate email: divs87_nair@yahoo.co.in