SPSS Syntax for Missing Value Imputation in Test and Questionnaire Data

Abstract

A well-known problem in the analysis of test and questionnaire data is that some item scores may be missing. Advanced methods for the imputation of missing data are available, such as multiple imputation under the multivariate normal model and imputation under the saturated logistic model (Schafer, 1997). Accompanying software was made available by, for example, Schafer (1998a, 1998b) and in SOLAS (2001) and S-Plus 6 for Windows (2001). However, these methods and software may be too complicated for a typical psychological researcher, and for the imputation of his or her missing data, he or she depends on the help of a trained statistician. If available, this statistician may not always have enough time or may not be an experienced software user, so the researcher may decide to simply delete all incomplete observations. To help researchers impute scores using simple methods, two SPSS subroutines were written. The aim of these subroutines is that researchers can apply them easily within SPSS and without experienced help. The subroutine "tw" performs two-way imputation, and the subroutine "rf" performs responsefunction imputation. Two-way imputation and response-function imputation are described by Sijtsma and Van der Ark (2003). Simulation studies by Van der Ark and Sijtsma (in press) indicate that these imputation methods work rather well when applied to an approximately unidimensional set of items (i.e., the items measure the same construct). The subroutines allow the researcher to transform an SPSS data file with missing values (an incomplete data file) into an SPSS data file without missing values (a completed data file). The researcher can use the completed data file for further analysis. To run the subroutines, one must select the variables containing the missing scores that need to be imputed, and some optional arguments also can be specified. For two-way imputation, the most important optional argument pertains to changing or removing the random error that is added to the imputed values by default. For response-function imputation, the most important optional argument pertains to changing the minimum group size used for estimating the response function (see Sijtsma & Van der Ark, 2003).

Cognitive and anxiety symptoms in screening for clinical depression in diabetes A systematic examination of diagnostic performances of the HADS and BDI-SF

“…Prior to the analyses, missing data were imputed by means of two-way imputations (Van Ginkel and Van der Ark, 2005). We performed logistic regressions to examine the ability of the scales to predict the odds of clinical depression.…”

The Social Thoughts and Beliefs Scale: Psychometric Properties and its Relation with Interpersonal Functioning in a Non-Clinical Sample

“…Researchers have developed measures assessing specific cognitive dimensions believed to be associated with social anxiety (e.g., Fear of Negative Evaluation Scale; Watson and Friend 1969). The Social Thoughts and Beliefs Scale (STABS; Turner et al 2003) was recently developed using an inductive approach to scale construction (Burisch 1984) to assess a broader domain of cognitions associated with social anxiety than extant measures and appears to measure thoughts that individuals typically have when encountering social situations.…”

“…Items were reduced through an exploratory factor analysis using data from patients with social anxiety disorder and other anxiety disorders. The final 21-item version of the measure was validated on a large clinical sample, including individuals with social anxiety disorder, with another anxiety disorder, or with no disorders (Turner et al 2003). Turner et al (2003) identified a two-factor solution underlying the 21 items of the STABS.…”

“…The final 21-item version of the measure was validated on a large clinical sample, including individuals with social anxiety disorder, with another anxiety disorder, or with no disorders (Turner et al 2003). Turner et al (2003) identified a two-factor solution underlying the 21 items of the STABS. The first factor, labeled ''Social Comparison'' (SC), represented thoughts that an individual may have about others being more socially proficient than s/he is.…”

Multiple Imputation of Missing Values Using the Response Function Method Based on a Data Set of the Health Assessment Questionnaire Disability Index

“…The R codes used in this study will be provided by the authors upon request with no expiration date (the RF imputation used in this study is also available as SPSS syntax that is freely downloadable from [http:// spitswww.uvt.nl/~avdrark/research/research.htm]). [23] …”