Efficient treatment allocation in 2 × 2 cluster randomized trials, when costs and variances are heterogeneous.

Typically, clusters and individuals in cluster randomized trials are allocated across treatment conditions in a balanced fashion. This is optimal under homogeneous costs and outcome variances. However, both the costs and the variances may be heterogeneous.

The effect of heterogeneous variance on efficiency and power of cluster randomized trials with a balanced 2 × 2 factorial design.

Sample size calculation for cluster randomized trials (CRTs) with a [Formula: see text] factorial design is complicated due to the combination of nesting (of individuals within clusters) with crossing (of two treatments). Typically, clusters and individuals are allocated across treatment conditions in a balanced fashion, which is optimal under homogeneity of variance. However, the variance is likely to be heterogeneous if there is a treatment effect.

Optimal and maximin sample sizes for multicentre cost-effectiveness trials.

This paper deals with the optimal sample sizes for a multicentre trial in which the cost-effectiveness of two treatments in terms of net monetary benefit is studied. A bivariate random-effects model, with the treatment-by-centre interaction effect being random and the main effect of centres fixed or random, is assumed to describe both costs and effects. The optimal sample sizes concern the number of centres and the number of individuals per centre in each of the treatment conditions.

Sample size calculation in cost-effectiveness cluster randomized trials: optimal and maximin approaches.

In this paper, the optimal sample sizes at the cluster and person levels for each of two treatment arms are obtained for cluster randomized trials where the cost-effectiveness of treatments on a continuous scale is studied. The optimal sample sizes maximize the efficiency or power for a given budget or minimize the budget for a given efficiency or power. Optimal sample sizes require information on the intra-cluster correlations (ICCs) for effects and costs, the correlations between costs and effects at individual and cluster levels, the ratio of the variance of effects translated into costs to the variance of the costs (the variance ratio), sampling and measuring costs, and the budget.

Bayesian design for dichotomous repeated measurements with autocorrelation.

In medicine and health sciences, binary outcomes are often measured repeatedly to study their change over time. A problem for such studies is that designs with an optimal efficiency for some parameter values may not be efficient for other values. To handle this problem, we propose Bayesian designs which formally account for the uncertainty in the parameter values for a mixed logistic model which allows quadratic changes over time.

Efficient treatment allocation in two-way nested designs.

Cluster randomized and multicenter trials sometimes combine two treatments A and B in a factorial design, with conditions such as A, B, A and B, or none. This results in a two-way nested design. The usual issue of sample size and power now arises for various clinically relevant contrast hypotheses.

Evaluation of the Hearing Aid Rehabilitation Questionnaire in Dutch: Examination of its Psychometric Properties and Potential Use as a Screening Instrument.

Items pertaining to hearing and hearing aids from the Hearing Aid Rehabilitation Questionnaire were applied to a heterogeneous sample of Dutch patients aged 55 years and more to evaluate their potential use in hearing screening. Subjects aged 55+ were recruited from a large general practitioners practice to participate. Three groups were formed: a group of 63 persons with a hearing aid, a group of 64 without a hearing aid but with sufficient hearing impairment to qualify for hearing aid reimbursement, and a group of 85 non-hearing impaired persons.

The effect of guiding questions on students' performance and attitude towards statistics.

Background: In this study, the effect of guidance on students' performance was investigated. This effect was hypothesized to be manifested through a reduction of cognitive load and enhancement of self-explanations.

Aim: The goal of this study was to investigate the effect of guiding questions on students' understanding of statistics.

Too many cohorts and repeated measurements are a waste of resources.

Objective: Researchers in Health Sciences and Medicine often use cohort designs to study treatment effects and changes of outcome variables over time period. The costs of these studies can be reduced by choosing an optimal number of repeated measurements over time and by selecting cohorts of subjects more efficiently with optimal design procedures. The objective of this study is to provide evidence on how to design large-scale cohort studies with budget constraints as efficiently as possible.

Optimal design for nonlinear estimation of the hemodynamic response function.

Subject-specific hemodynamic response functions (HRFs) have been recommended to capture variation in the form of the hemodynamic response between subjects (Aguirre et al., [ 1998]: Neuroimage 8:360-369). The purpose of this article is to find optimal designs for estimation of subject-specific parameters for the double gamma HRF.

The effect of directive tutor guidance on students' conceptual understanding of statistics in problem-based learning.

Background: Education is aimed at students reaching conceptual understanding of the subject matter, because this leads to better performance and application of knowledge. Conceptual understanding depends on coherent and error-free knowledge structures. The construction of such knowledge structures can only be accomplished through active learning and when new knowledge can be integrated into prior knowledge.

Optimal design of multi-subject blocked fMRI experiments.

The design of a multi-subject fMRI experiment needs specification of the number of subjects and scanning time per subject. For example, for a blocked design with conditions A or B, fixed block length and block order ABN, where N denotes a null block, the optimal number of cycles of ABN and the optimal number of subjects have to be determined. This paper presents a method to determine the optimal number of subjects and optimal number of cycles for a blocked design based on the A-optimality criterion and a linear cost function by which the number of cycles and the number of subjects are restricted.

ODmixed: a tool to obtain optimal designs for heterogeneous longitudinal studies with dropout.

ODMixed is a computer program to obtain optimal designs for linear mixed models of longitudinal studies. These designs account for heterogeneous correlated errors and for data with dropout. Designs are compared by using relative efficiencies, e.

Robustness of optimal design of fMRI experiments with application of a genetic algorithm.

In this paper we apply the genetic algorithm developed by Kao et al. (2009) to find designs which are robust against misspecification of the error autocorrelation. Two common optimality criteria, the A-optimality criterion and the D-optimality criterion, based upon a general linear model are employed to obtain locally optimal designs for a given value of the autocorrelation.

A cluster-randomized trial of an educational intervention to reduce the use of physical restraints with psychogeriatric nursing home residents.

Objectives: To investigate the effects of an educational intervention on the use of physical restraints with psychogeriatric nursing home residents.

Design: Cluster-randomized trial.

Setting: Fifteen psychogeriatric nursing home wards in the Netherlands.

An item response theory-based assessment of the pain assessment checklist for Seniors with Limited Ability to Communicate (PACSLAC).

Unlabelled: Pain is often undetected in older people with dementia partly due to a deterioration of cognitive functioning. Observational scales enable the measurement of pain by registering physiological changes, facial expressions, or behaviors. Previous research showed that the Pain Assessment Checklist for Seniors with Limited Ability to Communicate (PACSLAC) is especially useful to measure pain in older people with dementia.

Interactive computer program for optimal designs of longitudinal cohort studies.

Many large scale longitudinal cohort studies have been carried out or are ongoing in different fields of science. Such studies need a careful planning to obtain the desired quality of results with the available resources. In the past, a number of researches have been performed on optimal designs for longitudinal studies.

Optimal designs for one- and two-color microarrays using mixed models: a comparative evaluation of their efficiencies.

Comparative studies between the one- and two-color microarrays provide supportive evidence for similarities of results on differential gene expression. So far, no design comparisons between the two platforms have been undertaken. With the objective of comparing optimal designs of one- and two-color microarrays in their statistical efficiencies, techniques of design optimization were applied within a mixed model framework.

The prevalence of pain in nursing home residents with dementia measured using an observational pain scale.

Background: Studies on pain and pain prevalence in older people with dementia are limited compared to those on cognitively intact older people. Pain prevalence rates in older people with dementia are estimated to be between 28% and 83%.

Aims: This study aimed to explore pain prevalence in nursing home residents with dementia using observational scale PACSLAC-D, and to identify the association between pain prevalence and (dementia) demographic parameters such as cognitive status, gender, analgesic use and co-morbidity.

Preventing the use of physical restraints on residents newly admitted to psycho-geriatric nursing home wards: a cluster-randomized trial.

Background: Although there is an urgent need for restraint-free care, the number of randomized clinical trials on preventing or reducing physical restraints has been limited.

Objectives: To investigate the effectiveness of an educational intervention to prevent the use of physical restraints on residents newly admitted to psycho-geriatric nursing home wards.

Design: Cluster-randomized trial.

D-optimal cohort designs for linear mixed-effects models.

The D-optimality criterion is used to construct optimal designs for different numbers of independent cohorts, which constitute a number of repeated measurements per subject over time. A cost function for longitudinal data is proposed, and the optimality criterion is optimized taking into account the cost of the study. First, an optimal number of design points for a given number of cohorts and cost was identified.

Nursing staff knowledge and beliefs about pain in elderly nursing home residents with dementia.

Background: Aging is known to be associated with a high prevalence (up to 80%) of persistent pain among residents of nursing homes. However, even with high pain prevalence rates, nursing home residents are at risk for undertreatment. Knowledge deficits and beliefs among nurses influence staff behaviour in pain assessment and management.

Optimal designs for clinical trials with second-order polynomial treatment effects.

The effect of adding intermediate measures on the efficiency of treatment effect estimation is considered for a second-order polynomial treatment effect, equidistant time-points, different covariance structures and two optimality criteria, assuming either a fixed sample size or a fixed budget. The benefit of adding intermediate measures (at the expense of subjects) depends strongly on the assumed covariance structure and is hardly affected by the two used optimality criteria (Ds or c). For a fixed sample size, the increase in efficiency by adding intermediate measures is large for a compound symmetric structure and small for a first-order auto-regressive structure.

The effectiveness of massage with and without dimethyl sulfoxide in preventing pressure ulcers: a randomized, double-blind cross-over trial in patients prone to pressure ulcers.

Background: Although guidelines advise against massage, it is one of the methods widely regarded and used by nurses to prevent pressure ulcers (PU).

Objectives: The purpose of this study was to examine the effectiveness of different variations of massage in preventing pressure ulcers.

Methods: A randomized, double-blind cross-over design, in which patients of nursing homes who are prone to PU underwent two of the three possible interventions; 'position changes only', 'massaging with an indifferent cream' and 'massaging with a dimethyl sulfoxide (DMSO) cream'.

Organisational determinants of the use of physical restraints: a multilevel approach.

This paper reports a study of the relationship between the use of physical restraints with psycho-geriatric nursing home residents and the characteristics of organisations and residents. It is hypothesised that impairment in residents and organisational characteristics, such as a high workload of nursing staff and a low full-time equivalent (FTE) ratio on the wards, are associated with increased restraint use. In a cross-sectional study involving 15 Dutch psycho-geriatric nursing home wards, 432 residents were selected for participation, of which 371 actually participated.