P.G.M. Van der Heijden

Unidimensionality and reliability under Mokken scaling of the Dutch language version of the SF-36

The sub-scales of the SF-36 in the Dutch National Study are investigated with respect to unidimensionality and reliability. It is argued that these properties deserve separate treatment. For unidimensionality we use a non-parametric model from item response theory, called the Mokken scaling model, and compute the corresponding scalability coefficients. We estimate reliability under the Mokken model, assuming that the items are double homogeneous, and compare it to Cronbachs α. The scalability of the sub-scale general health perceptions is medium (H = 0.46), and for the other sub-scales it is strong (H ≥ 0.6). The reliability in terms of α indicates that all sub-scales can be used in basic research ( > 0.70), but that only physical functioning can be used for clinical applications of quality of life ( > 0.90). The relative merits of our approach are discussed.

Prevalence of use of performance enhancing drugs by fitness centre members

Studies on the use of performance enhancing drugs (PED) in fitness centres rely predominately on conventional survey methods using direct questioning. However, research indicates that direct questioning of sensitive information is characterized by under-reporting. The aim of the present study was to contrast direct questioning of different types of PED use by Dutch fitness centre members with results obtained with the Randomized Response Technique (RRT). Questionnaires were conducted among members of fitness centres. PED were classified into the following categories: anabolic steroids, prohormones, substances to counteract side-effects, growth hormone and/or insulin, stimulants (to reduce weight), and miscellaneous substances. A total of 718 athletes from 92 fitness centres completed the questionnaire. The conventional method resulted in prevalences varying between 0% and 0.4% for the different types of PED with an overall prevalence of 0.4%. RRT resulted in prevalences varying between 0.8% and 4.8% for the different types of PED with an overall prevalence of 8.2%. The overall prevalence of the two survey methods differed significantly. The current study showed that the conventional survey method using direct questioning led to an underestimation of the prevalence. Based on the RRT results, the percentage of users of PED among members of fitness centres is approximately 8.2%. Stimulants to lose weight had the highest prevalence, even higher than anabolic steroids. The key task for future preventive health work is to not only focus on anabolic steroid use, but also include interventions focusing on the use of stimulants to lose weight.

PTSD in persons with burns: An explorative study examining relationships with attributed responsibility, negative and positive emotional states

A sample of 90 persons who had been hospitalized for severe burns were interviewed 1-4 years after the incident. Current DSM-IV post-traumatic stress disorder (PTSD) was assessed with the Composite International Diagnostic Interview. Perceived attributed responsibility and related positive and negative emotional states were examined using a semi-structured interview. Findings showed that PTSD was established in 8% of the participants and partial PTSD in 13%. In a homogeneity analysis (HOMALS), PTSD was associated with the attribution of responsibility for the incident to impersonal relationships and with a negative emotional state. The absence of (partial) PTSD was associated with the attribution of responsibility to close relationships, internal and circumstance-related attribution of responsibility and neutral or forgiving feelings. In logit analyses, both emotional state as well as attributed responsibility are significantly related to (partial) PTSD. However, the model including emotional state showed to have the best fit. Although further research is needed, these results may indicate that professionals working in burn care should consider the emotional state in relation to perceived attribution of responsibility when considering PTSD. Promoting forgiveness may be a beneficial strategy in dealing with post-traumatic stress reactions.

An Extended Study Into the Relationship Between Correspondence Analysis and Latent Class Analysis

Researchers dealing with frequency data today can choose from a vast range of methods, descriptive and inferential. Two such well-known and useful methods are correspondence analysis and latent class analysis. Although these two methods were initially used for different research objectives, they are mathematically related to each other. Relations between these methods, however, have only been reported in the literature regarding the bivariate case. In this paper, we extend the study of such relations to the multivariate case. In particular the multivariate X latent class model is shown to imply the (relatively new) joint multivariate correspondence model with X − 1 positive eigenvalues. Such relations allow the underlying methods to be treated as variants of the same conceptual idea, providing some new meaningful aspects, which may help researchers better interpret the findings of their investigation.

Correspondence Analysis, with Special Attention to the Analysis of Panel Data and Event History Data

Correspondence Analysis, with Special Attention to the Analysis of Panel Data and Event History Data Peter G. M . van der Heyden; Jan de Leeuw Sociological Methodology, V o l . 19. (1989), pp. 43-87. Stable URL: http://links.jstor.org/sici?sici=0081-1750%281989%2919%3C43%3ACAWSAT%3E2.0.CO%3B2-l Sociological Methodology is currently published by American Sociological Association. Your use of the JSTOR archive indicates your acceptance of JSTORs Terms and Conditions of Use, available at http://www.jstor.org/about/terms.html. JSTORs Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http: // w w w .j s tor. org/j oum al s/as a. h tml. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is an independent not-for-profit organization dedicated to creating and preserving a digital archive of scholarly journals. For more information regarding JSTOR, please contact suppoit@jstor.org. http : // w w w .j s tor. org/ Sat Sep 30 12:02:47 2006

Semiparametric models for capture–recapture studies with covariates

A 4exible method for modelling capture–recapture data with continuous covariates that describe heterogeneous catchability is developed. The well established generalized additive modelling framework is used. An estimator of population size is developed using this method. The performance of the method is demonstrated using neural tube defect capture–recapture data from the Netherlands, with the birth weight of a child as a covariate. The parametric bootstrap is used for variance estimation. c 2003 Elsevier B.V. All rights reserved.

People born in the Middle East but residing in the Netherlands: invariant population size estimates and the role of active and passive covariates

Including covariates in loglinear models of population registers improves population size estimates for two reasons. First, it is possible to take heterogeneity of inclusion probabilities over the levels of a covariate into account; and second, it allows subdivision of the estimated population by the levels of the covariates, giving insight into characteristics of individuals that are not included in any of the registers. The issue of whether or not marginalizing the full table of registers by covariates over one or more covariates leaves the estimated population size estimate invariant is intimately related to collapsibility of contingency tables [Biometrika 70 (1983) 567–578]. We show that, with information from two registers, population size invariance is equivalent to the simultaneous collapsibility of each margin consisting of one register and the covariates. We give a short path characterization of the loglinear model which describes when marginalizing over a covariate leads to different population size estimates. Covariates that are collapsible are called passive, to distinguish them from covariates that are not collapsible and are termed active. We make the case that it can be useful to include passive covariates within the estimation model, because they allow a finer description of the population in terms of these covariates. As an example we discuss the estimation of the population size of people born in the Middle East but residing in the Netherlands

The Influence of Misspecification of the Heteroscedasticity on Multilevel Regression Parameter and Standard Error Estimates

Like in ordinary regression models, in multilevel analysis, homoscedasticity of the residual variances is an assumption that is mostly unchecked. However, in experimental research, the residual variance component at level two may differ in the experimental and the control condition, leading to heteroscedastic second level variances. Using a simulation study, the consequences of ignoring second level heteroscedasticity on the estimation of the fixed and random parameters and their standard errors was investigated. It was found that the standard error of the second level variance is underestimated, but that the estimated fixed parameters of the independent variables, the first level variance and their standard errors are mostly unbiased.

Capture-recapture to estimate criminal populations

Methodology is presented that allows to estimate the size of population from a single register, such as a police register of offenders. A capture-recapture variable is constructed from Dutch police records and is a count of the police contacts for a violation. A population size estimate is derived assuming that each count is a realization of a Poisson distribution and that the Poisson parameters are related to covariates through the truncated Poisson regression model or variants of this model. As an example, estimates for perpetrators of domestic violence are presented. It is concluded that the methodology is useful, provided it is used with care.

Some examples of latent budget analysis and its extensions.

Latent budget analysis is a mixture model for the analysis of two-way tables with frequency data where interest lies in the relationship between the rows and the columns. The frequencies are replaced by conditional proportions. Hence each row in the table has nonnegative entries that add up to 1. Such rows are called budgets and each budget forms the observed distribution of the column variable. The latent budget model assumes that a small number of latent distributions (latent budgets) have generated the observed distributions (observed budgets) in the two-way table. After briefly introducing the latent budget model three examples are given. The first is a straightforward example of the use of the model to analyze sentence endings in the works of Plato. The second example is a study of the relationship between ethnic background and the types of trades started up by people in two cities in the Netherlands. Because the main question here is whether this relationship is the same in both cities, extensions of the latent budget model are discussed that allow for homogeneity constraints over different subtables. The third example is a study of a well known Dutch cohort, namely the SMVO-cohort. Here the dependent variable is the type of secondary education children choose as a function of their IQ, their sex and the profession of their fathers. The mixing parameters in the latent budget model are a function of the explanatory variables, and this function is defined by a multinomial logit model. Van der Heijden et al. Latent Budget Analysis 3