Papers by Math J. J. M. Candel
Tobacco Control, 2021
BackgroundStudies demonstrated that adolescent e-cigarette use is associated with subsequent toba... more BackgroundStudies demonstrated that adolescent e-cigarette use is associated with subsequent tobacco smoking, commonly referred to as thegateway effect. However, most studies only investigated gateways from e-cigarettes to tobacco smoking. This study replicates a cornerstone study revealing a positive association between both adolescent e-cigarette use and subsequent tobacco use; and tobacco and subsequent e-cigarette use in the Netherlands and Flanders.DesignThe longitudinal design included baseline (n=2839) and 6-month (n=1276) and 12-month (n=1025) follow-up surveys among a school-based cohort (mean age: 13.62). Ten high schools were recruited as a convenience sample. The analyses involved (1) associations of baseline e-cigarette use and subsequent tobacco smoking among never smokers; (2) associations of e-cigarette use frequency at baseline and tobacco smoking frequency at follow-up; and (3) the association of baseline tobacco smoking and subsequent e-cigarette use among non-use...
Additional file 5. Response-percentages additional questions. Response-percentages of each profes... more Additional file 5. Response-percentages additional questions. Response-percentages of each professional group per additional question.
Additional file 6. Lowest ranking ethical climate items. Overview of the lowest ranking ethical c... more Additional file 6. Lowest ranking ethical climate items. Overview of the lowest ranking ethical climate items in the extended EDMCQ per profession.
Biometrical Journal, 2021
Cluster randomized trials evaluate the effect of a treatment on persons nested within clusters, w... more Cluster randomized trials evaluate the effect of a treatment on persons nested within clusters, with clusters being randomly assigned to treatment. The optimal sample size at the cluster and person level depends on the study cost per cluster and per person, and the outcome variance at the cluster and the person level. The variances are unknown in the design stage and can differ between treatment arms. As a solution, this paper presents a Maximin design that maximizes the minimum relative efficiency (relative to the optimal design) over the variance parameter space, for trials with two treatment arms and a quantitative outcome. This maximin relative efficiency design (MMRED) is compared with a published Maximin design which maximizes the minimum efficiency (MMED). Both designs are also compared with the optimal designs for homogeneous costs and variances (balanced design) and heterogeneous costs and homogeneous variances (cost‐conscious design), for a range of variances based upon three published trials. Whereas the MMED is balanced under high uncertainty about the treatment‐to‐control variance ratio, the MMRED then tends towards a balanced budget allocation between arms, leading to an unbalanced sample size allocation if costs are heterogeneous, similar to the cost‐conscious design. Further, the MMRED corresponds to an optimal design for an intraclass correlation (ICC) in the lower half of the assumed ICC range (optimistic), whereas the MMED is the optimal design for the maximum ICC within the ICC range (pessimistic). Attention is given to the effect of the Welch–Satterthwaite degrees of freedom for treatment effect testing on the design efficiencies.
International Journal of Environmental Research and Public Health, 2019
In 2016, the Netherlands was required to introduce new European Union (EU)’s (pictorial) tobacco ... more In 2016, the Netherlands was required to introduce new European Union (EU)’s (pictorial) tobacco health warnings. Our objective was to describe the pathways through which the new EU tobacco health warnings may influence quit attempts and smoking cessation among Dutch smokers. Longitudinal data from 2016 and 2017 from the International Tobacco Control (ITC) Netherlands Survey were used. Smokers who participated in both surveys were included (N = 1017). Structural equation modeling was applied to examine the hypothesized pathways. Health warning salience was positively associated with more health worries (β = 0.301, p < 0.001) and a more positive attitude towards quitting (β = 0.180, p < 0.001), which, in turn, were associated with a stronger quit intention (health worries: β = 0.304, p < 0.001; attitude: β = 0.340, p < 0.001). Quit intention was a strong predictor of quit attempts (β = 0.336, p = 0.001). Health warning salience was also associated with stronger perceived ...
Statistics in Medicine, 2018
International Journal of Epidemiology, 2018
Computational Statistics, 2018
Statistics in Medicine, 2007
Statistics in Medicine, 2018
Psychological methods, 2021
To prevent mistakes in psychological assessment, the precision of test norms is important. This c... more To prevent mistakes in psychological assessment, the precision of test norms is important. This can be achieved by drawing a large normative sample and using regression-based norming. Based on that norming method, a procedure for sample size planning to make inference on Z-scores and percentile rank scores is proposed. Sampling variance formulas for these norm statistics are derived and used to obtain the optimal design, that is, the optimal predictor distribution, for the normative sample, thereby maximizing precision of estimation. This is done under five regression models with a quantitative and a categorical predictor, differing in whether they allow for interaction and nonlinearity. Efficient robust designs are given in case of uncertainty about the regression model. Furthermore, formulas are provided to compute the normative sample size such that individuals' positions relative to the derived norms can be assessed with prespecified power and precision. (PsycInfo Database R...
In the marketing literature, the influence of a place-of-origin indication on the evaluation of p... more In the marketing literature, the influence of a place-of-origin indication on the evaluation of products has been studied with little consideration for the image of the place of origin as a separate construct. Although effects of a place-of-origin indication have been found, it is still unclear what components make up the image of a place of origin, and how they determine consumers' evaluations of products originating from that place. In this paper, we propose and empirically test a conceptual framework that addresses these issues. More specifically, we examine how the image of a region influences the perceptions of and preferences for products.
Resultaten van consumentenonderzoek betreffende de keuze van vleesprodukten uit overwegingen van ... more Resultaten van consumentenonderzoek betreffende de keuze van vleesprodukten uit overwegingen van kwaliteit, imago, gebruiksgemak en de wijze, waarop het geproduceerd is (hormoongebruik, dier- en milieuvriendelijk)
Computational and Mathematical Methods in Medicine
If there are no carryover effects, AB/BA crossover designs are more efficient than parallel (A/B)... more If there are no carryover effects, AB/BA crossover designs are more efficient than parallel (A/B) and extended parallel (AA/BB) group designs. This study extends these results in that (a) optimal instead of equal treatment allocation is examined, (b) allowance for treatment-dependent outcome variances is made, and (c) next to treatment effects, also treatment by period interaction effects are examined. Starting from a linear mixed model analysis, the optimal allocation requires knowledge on intraclass correlations in A and B, which typically is rather vague. To solve this, maximin versions of the designs are derived, which guarantee a power level across plausible ranges of the intraclass correlations at the lowest research costs. For the treatment effect, an extensive numerical evaluation shows that if the treatment costs of A and B are equal, or if the sum of the costs of one treatment and measurement per person is less than the remaining subject-specific costs (e.g., recruitment c...
Nicotine & Tobacco Research
Introduction Financial incentives effectively increase smoking cessation rates, but it is unclear... more Introduction Financial incentives effectively increase smoking cessation rates, but it is unclear via which psychological mechanisms incentives influence quit behavior. The current study examines how receiving financial incentives for smoking cessation leads to quitting smoking and investigates several mediators and moderators of that relationship. Aims and Methods The study sample consisted of 604 tobacco-smoking employees from 61 companies in the Netherlands who completed a baseline and follow-up questionnaire. The current study is a secondary analysis from a cluster randomized trial where employees received smoking cessation group counseling at the workplace. Participants in the intervention group additionally received financial incentives of €350 in total for 12-month continuous smoking abstinence. We used a two-level path analysis to test a model that assesses the effects of financial incentives through smoking cessation program evaluation, medication use, nicotine replacement ...
Health Psychology and Behavioral Medicine
Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco, Jan 3, 2017
The aim of the study was to compare the construct validity and the predictive validity of three i... more The aim of the study was to compare the construct validity and the predictive validity of three instruments to measure intention to quit smoking: a Stages of Change measure, the Motivation To Stop Scale (MTSS) and a Likert scale. We used the Theory of Planned Behaviour as theoretical framework. We used data from the International Tobacco Control (ITC) Netherlands Survey. We included smokers who participated in three consecutive survey waves (n=980). We measured attitude, subjective norm, and perceived behavioural control in 2012, intention to quit with three instruments in 2013, and having made a quit attempt in the last year in 2014. We conducted Structural Equation Modelling with three models for the instruments of intention separately, and with one model that included the three instruments simultaneously. All three instruments of intention were significantly and positively related to attitude and perceived behavioural control but none was related to subjective norm. All three ins...
American journal of medical genetics. Part A, Sep 1, 2016
Many studies have attempted to establish the genotype-phenotype correlation in Rett syndrome (RTT... more Many studies have attempted to establish the genotype-phenotype correlation in Rett syndrome (RTT). Cardiorespiratory measurements provide robust objective data, to correlate with each of the different clinical phenotypes. It has important implications for the management and treatment of this syndrome. The aim of this study was to correlate the genotype with the quantitative cardiorespiratory data obtained by neurophysiological measurement combined with a clinical severity score. This international multicenter study was conducted in four European countries from 1999 to 2012. The study cohort consisted of a group of 132 well-defined RTT females aged between 2 and 43 years with extended clinical, molecular, and neurophysiological assessments. Diagnosis of RTT was based on the consensus criteria for RTT and molecular confirmation. Genotype-phenotype analyses of clinical features and cardiorespiratory data were performed after grouping mutations by the same type and localization or havi...
Health Education, 2015
Purpose – Intersectoral collaboration is often a prerequisite for effective interventions in publ... more Purpose – Intersectoral collaboration is often a prerequisite for effective interventions in public health. The purpose of this paper is to assess the facilitating and hindering conditions regarding intersectoral collaboration between health authorities, public health services (PHSs), public services stakeholders (PPSs) and the education sector in comprehensive school health promotion (CSHP) in the Netherlands. Design/methodology/approach – CSHP collaborations in five Dutch regions were studied using a questionnaire based on the DIagnosis of Sustainable Collaboration (DISC) model, focusing on: change management; perceptions, intentions and actions of collaborating parties; project organization; and factors in the wider context. Univariate and multivariate analyses with bootstrapping were applied to 106 respondents (62 percent response). Findings – A similar pattern of facilitating and hindering conditions emerged for the five regions, showing positive perceptions, but fewer positive...
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Papers by Math J. J. M. Candel