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- Klaas Sijtsma
- Psychometrika
- 2009

This discussion paper argues that both the use of Cronbach's alpha as a reliability estimate and as a measure of internal consistency suffer from major problems. First, alpha always has a value, which cannot be equal to the test score's reliability given the interitem covariance matrix and the usual assumptions about measurement error. Second, in practice,… (More)

Kerry Kravec for assistance with computations for examples in Section 4, and we thank Mark Schervish for a discussion greatly simplifying one of the monotonicity conditions discussed in Section 4. Abstract In recent years, as cognitive theories of learning and instruction have become richer, and computational methods to support assessment have become more… (More)

- C A Bernaards, K Sijtsma
- Multivariate behavioral research
- 2000

This study deals with the influence of each of twelve imputation methods and two methods using the EM algorithm on the results of maximum likelihood factor analysis as compared with results obtained from the complete data factor analysis (no missing scores). Complete questionnaire rating scale data were simulated and, next, missing item scores were created… (More)

- Joost R van Ginkel, L Andries van der Ark, Klaas Sijtsma
- Multivariate behavioral research
- 2007

The performance of five simple multiple imputation methods for dealing with missing data were compared. In addition, random imputation and multivariate normal imputation were used as lower and upper benchmark, respectively. Test data were simulated and item scores were deleted such that they were either missing completely at random, missing at random, or… (More)

- Rob R Meijer, Iris J L Egberink, Wilco H M Emons, Klaas Sijtsma
- Journal of personality assessment
- 2008

We illustrate the usefulness of person-fit methodology for personality assessment. For this purpose, we use person-fit methods from item response theory. First, we give a nontechnical introduction to existing person-fit statistics. Second, we analyze data from Harter's (1985) Self-Perception Profile for Children (Harter, 1985) in a sample of children… (More)

- Klaas Sijtsma, L Andries van der Ark
- Multivariate behavioral research
- 2003

This article first discusses a statistical test for investigating whether or not the pattern of missing scores in a respondent-by-item data matrix is random. Since this is an asymptotic test, we investigate whether it is useful in small but realistic sample sizes. Then, we discuss two known simple imputation methods, person mean (PM) and two-way (TW)… (More)

- Jeroen K. Vermunt, Joost R. van Ginkel, Andries van der Ark, Klaas Sijtsma
- 2008

We propose using latent class analysis as an alternative to log-linear analysis for the multiple imputation of incomplete categorical data. Similar to log-linear models, latent class models can be used to describe complex association structures between the variables used in the imputation model. However, unlike log-linear models, latent class models can be… (More)

- Joost R van Ginkel, L Andries van der Ark, Klaas Sijtsma
- The British journal of mathematical and…
- 2007

Multiple imputation under a two-way model with error is a simple and effective method that has been used to handle missing item scores in unidimensional test and questionnaire data. Extensions of this method to multidimensional data are proposed. A simulation study is used to investigate whether these extensions produce biased estimates of important… (More)

- Joost R. Van Ginkel, L. Andries Van der Ark, Klaas Sijtsma, Jeroen K. Vermunt
- Computational Statistics & Data Analysis
- 2007

We give a historical introduction to item response theory, which places the work of Thurstone, Lord, Guttman and Coombs in a present-day perspective. The general assumptions of modern item response theory, local independence and monotonicity of response functions, are discussed, followed by a general framework for estimating item response models. Six… (More)