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As in all surveys, there are two general types of missing data in SIPP: unit nonresponse and item nonresponse. Unit nonresponse occurs in SIPP when one or more of the people residing at a sample address are not interviewed and no proxy interview is obtained. This can happen for a number of reasons, described in Chapter 2 of the SIPP Users' Guide. Most types of unit nonresponse are dealt with through weighting adjustments (see Chapters 2 and 8 of the SIPP Users' Guide). However, the data editing and statistical imputation procedures described in this chapter are used with one type of unit nonresponse: Type Z noninterviews, which occur when an interview is obtained from at least one household member but interviews are not obtained from one or more other sample persons in that household.1 Prior to the 1996 Panel and in some instances in the 1996 Panel, the method used to adjust for person-level noninterviews in the core wave files is known as Type Z imputation, which is discussed below.
Item nonresponse occurs when a respondent completes most of the questionnaire but does not answer one or more individual questions. Item nonresponse data in SIPP occur under the following circumstances:
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1 That can happen either because people refuse to be interviewed or because they are unavailable for the interview
and a proxy interview is not obtained.
2 Prior to the 1996 Panel, errors could also occur when data-entry workers were keying in results from the paper survey.
Missing Data Problems
Handling Missing Data
Data Editing and Imputation Goals
Effects of Imputed Data on Analysis
Processing SIPP Data
Confidentiality Procedures
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Page Last Modified: May 9, 2006
