In IHIS what does "not ascertained" mean for BIDIEV, PIPEV etc in 2000 and 2005?


In IHIS, I am looking at non-cigarette tobacco use for 2000 and 2005, i.e. variables BIDIEV, PIPEV, CIGAREV etc.

As well as the “NIU”, “don’t know” and “refused codes”, there are a considerable (and consistent) number of occurrences of code 8=“not ascertained”. I assume this is due to only a subsample answering this batch of questions.

I am planning to use crosstablualtion to generate some fairly simple tables showing prevalence of usage by various other factors. Would it be appropriate to omit those “not ascertained” codes from the analysis along with the NIUs?

Is the SAMPWEIGHT still the correct weighting to use?



A code of “Unknown - not ascertained” typically indicates that the respondent’s value for that question was blank, even though they were in the question’s universe. For example, this can occur if a sample adult does not complete the questionnaire or it can be caused by a recording error. Even if you exclude the “not ascertained” responses, it is still correct to use SAMPWEIGHT for the non-cigarette tobacco use variables.

Hope this helps.