[amelia] RE: Way to Do Missing Value Imputation But Also Have Structurally Missing Data Unhampered?

Thanks for the reply. Indeed you are correct about the "are you pregnant" analogy. There is no sensible answer to those questions for those people. Your solution to just impute everything, then know that particular cells is intriguing. On one hand, it is quite simple. On the other hand, I was under the impression that an iterative process went on behind the scenes in estimating the missing values. Your response leads me to believe that it is iterative in the sense that it only uses information from data that exists and does not substitute, then go through another iteration (think of a cluster analysis procedure where people are first assigned, then can move around a bit, depdenting upon what procedure you are using). Once again, many thanks for getting back with me so quickly. Zachary -----Original Message----- From: Gary King [mailto:king@harvard.edu] Sent: Friday, July 11, 2003 9:14 PM To: Feinstein, Zachary Cc: Amelia Listserv Subject: Re: Way to Do Missing Value Imputation But Also Have Structurally Mis sing Data Unhampered? a structural missing element would be the answer to the question "are you pregnant?" and the respondent is male. you don't ask the question because there is no sensible random variable that this answer would produce. if you havethis kind of problem, thenyou could merely impute this along with the rest but ignore the imputations for the structural zeros. however, maybe what you have instead is just questions you decided not to ask some respondents for lack of time. this is often called matrix sampling, and there's no problme both imputing and using theimputations from this setup. in fact, since you determine the missingness pattern, you know that the asumptions of amelia apply (assuming you choose the respondents in a sensible way of course). Gary On Fri, 11 Jul 2003, Feinstein, Zachary wrote: for the way X that define scale valued