Review of sample size determination methods for the intraclass correlation coefficient in the one-way analysis of variance model.

Reliability of measurement instruments providing quantitative outcomes is usually assessed by an intraclass correlation coefficient. When participants are repeatedly measured by a single rater or device, or, are each rated by a different group of raters, the intraclass correlation coefficient is based on a one-way analysis of variance model. When planning a reliability study, it is essential to determine the number of participants and measurements per participant (i.

Optimal two-stage sampling for mean estimation in multilevel populations when cluster size is informative.

To estimate the mean of a quantitative variable in a hierarchical population, it is logistically convenient to sample in two stages (two-stage sampling), i.e. selecting first clusters, and then individuals from the sampled clusters.

Assessing the Efficacy of MOTI-4 for Reducing the Use of Cannabis Among Youth in the Netherlands: A Randomized Controlled Trial.

The Moti-4 intervention, in which motivational interviewing, self-monitoring, and strengthening behavioral control are used, was developed in the Netherlands in response to several rapid assessments of problematic use of cannabis among vulnerable adolescents. The main goal of the study reported in this article was to determine whether the Moti-4 intervention was able to reduce two outcome measures pertaining to the level of cannabis use; the amount of Euros spent a week on cannabis and the mean number of cannabis joints (cigarettes) smoked in a week. In a randomized controlled trial (RCT) with a 6-month follow-up, 27 trained Dutch prevention workers recruited 71 Moti-4 participants and 60 controls assigned to usual care.

Repairing the efficiency loss due to varying cluster sizes in two-level two-armed randomized trials with heterogeneous clustering.

In two-armed trials with clustered observations the arms may differ in terms of (i) the intraclass correlation, (ii) the outcome variance, (iii) the average cluster size, and (iv) the number of clusters. For a linear mixed model analysis of the treatment effect, this paper examines the expected efficiency loss due to varying cluster sizes based upon the asymptotic relative efficiency of varying versus constant cluster sizes. Simple, but nearly cost-optimal, correction factors are derived for the numbers of clusters to repair this efficiency loss.

Exploring individual cognitions, self-regulation skills, and environmental-level factors as mediating variables of two versions of a Web-based computer-tailored nutrition education intervention aimed at adults: A randomized controlled trial.

Background: This study explored whether the determinants that were targeted in two versions of a Web-based computer-tailored nutrition education intervention mediated the effects on fruit, high-energy snack, and saturated fat intake among adults who did not comply with dietary guidelines.

Method: A RCT was conducted with a basic (tailored intervention targeting individual cognitions and self-regulation), plus (additionally targeting environmental-level factors), and control group (generic nutrition information). Participants were recruited from the general Dutch adult population and randomly assigned to one of the study groups.

Effectiveness of a systematic approach to promote intersectoral collaboration in comprehensive school health promotion-a multiple-case study using quantitative and qualitative data.

Background: We report on the longitudinal quantitative and qualitative data resulting from a two-year trajectory (2008-2011) based on the DIagnosis of Sustainable Collaboration (DISC) model. This trajectory aimed to support regional coordinators of comprehensive school health promotion (CSHP) in systematically developing change management and project management to establish intersectoral collaboration.

Methods: Multilevel analyses of quantitative data on the determinants of collaborations according to the DISC model were done, with 90 respondents (response 57 %) at pretest and 69 respondents (52 %) at posttest.

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.

Short- and medium-term efficacy of a Web-based computer-tailored nutrition education intervention for adults including cognitive and environmental feedback: randomized controlled trial.

Background: Web-based, computer-tailored nutrition education interventions can be effective in modifying self-reported dietary behaviors. Traditional computer-tailored programs primarily targeted individual cognitions (knowledge, awareness, attitude, self-efficacy). Tailoring on additional variables such as self-regulation processes and environmental-level factors (the home food environment arrangement and perception of availability and prices of healthy food products in supermarkets) may improve efficacy and effect sizes (ES) of Web-based computer-tailored nutrition education interventions.

Prevalence and reasons for use of electronic cigarettes among smokers: Findings from the International Tobacco Control (ITC) Netherlands Survey.

Background: Not much is known about how people in the Netherlands respond to electronic cigarettes (e-cigarettes); how many know about them, which people try them, keep using them and why, and what are changes over time regarding awareness and use?

Methods: We used samples of smokers aged 15 years and older from 2008 (n=1820), 2010 (n=1702), 2013 (n=1530), and 2014 (n=1550) as part of the International Tobacco Control (ITC) Netherlands Survey. Reasons for use and characteristics of smokers were examined using the sample from 2014. Logistic regression analyses were conducted to evaluate the associations between smoking-related variables with ever trying e-cigarettes and current e-cigarette use.

Sample size calculation for treatment effects in randomized trials with fixed cluster sizes and heterogeneous intraclass correlations and variances.

When comparing two different kinds of group therapy or two individual treatments where patients within each arm are nested within care providers, clustering of observations may occur in both arms. The arms may differ in terms of (a) the intraclass correlation, (b) the outcome variance, (c) the cluster size, and (d) the number of clusters, and there may be some ideal group size or ideal caseload in case of care providers, fixing the cluster size. For this case, optimal cluster numbers are derived for a linear mixed model analysis of the treatment effect under cost constraints as well as under power constraints.

Reducing alcohol use during pregnancy via health counseling by midwives and internet-based computer-tailored feedback: a cluster randomized trial.

Background: Effective interventions are needed to reduce neurobehavioral impairments in children due to maternal alcohol use during pregnancy. Currently, health-counseling interventions have shown inconsistent results to reduce prenatal alcohol use. Thus, more research using health counseling is needed to gain more knowledge about the effectiveness of this type of intervention on reducing alcohol use during pregnancy.

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.

Effects of a web-based tailored multiple-lifestyle intervention for adults: a two-year randomized controlled trial comparing sequential and simultaneous delivery modes.

Background: Web-based computer-tailored interventions for multiple health behaviors can have a significant public health impact. Yet, few randomized controlled trials have tested this assumption.

Objective: The objective of this paper was to test the effects of a sequential and simultaneous Web-based tailored intervention on multiple lifestyle behaviors.

Effects of a Web-based tailored intervention to reduce alcohol consumption in adults: randomized controlled trial.

Background: Web-based tailored interventions provide users with information that is adapted to their individual characteristics and needs. Randomized controlled trials assessing the effects of tailored alcohol self-help programs among adults are scarce. Furthermore, it is a challenge to develop programs that can hold respondents' attention in online interventions.

Acknowledging patient heterogeneity in economic evaluation : a systematic literature review.

Background And Objective: Patient heterogeneity is the part of variability that can be explained by certain patient characteristics (e.g. age, disease stage).

Calculating sample sizes for cluster randomized trials: we can keep it simple and efficient!

Objective: Simple guidelines for calculating efficient sample sizes in cluster randomized trials with unknown intraclass correlation (ICC) and varying cluster sizes.

Methods: A simple equation is given for the optimal number of clusters and sample size per cluster. Here, optimal means maximizing power for a given budget or minimizing total cost for a given power.

Preventing smoking relapse via Web-based computer-tailored feedback: a randomized controlled trial.

Background: Web-based computer-tailored approaches have the potential to be successful in supporting smoking cessation. However, the potential effects of such approaches for relapse prevention and the value of incorporating action planning strategies to effectively prevent smoking relapse have not been fully explored. The Stay Quit for You (SQ4U) study compared two Web-based computer-tailored smoking relapse prevention programs with different types of planning strategies versus a control group.

Lost productivity in four European countries among patients with rheumatic disorders: are absenteeism and presenteeism transferable?

Background: When national pharmacoeconomic guidelines are compared, different recommendations are identified on how to identify, measure and value lost productivity, leading to difficulties when comparing lost productivity estimates across countries. From a transferability point of view, the question arises of whether differences between countries regarding lost productivity are the result of using different calculation methods (methodological differences) or of other between-country differences. When lost productivity data differ significantly across countries, the transferability of lost productivity data across countries is hindered.

Pathways of change explaining the effect of smoke-free legislation on smoking cessation in The Netherlands. An application of the international tobacco control conceptual model.

Introduction: This study aims to test the pathways of change from individual exposure to smoke-free legislation on smoking cessation, as hypothesized in the International Tobacco Control (ITC) Conceptual Model.

Methods: A nationally representative sample of Dutch smokers aged 15 years and older was surveyed during 4 consecutive annual surveys. Of the 1,820 baseline smokers, 1,012 participated in the fourth survey.

Parallel, AA/BB, AB/BA and Balaam's design: efficient and maximin choices when testing the treatment effect in a mixed effects linear regression.

When examining the effect of treatment A versus B, there may be a choice between a parallel group design, an AA/BB design, an AB/BA cross-over and Balaam's design. In case of a linear mixed effects regression, it is examined, starting from a flexible function of the costs involved and allowing for subject dropout, which design is most efficient in estimating this effect. For no carry-over, the AB/BA cross-over design is most efficient as long as the dropout rate at the second measurement does not exceed 2ρ/(1 + ρ), ρ being the intraclass correlation.

Agreement between self-reports and on-site inspections of compliance with a workplace smoking ban.

Introduction: This study compares self-reports on compliance with a workplace smoking ban with on-site inspections of the same workplace, in the Netherlands, to assess the validity of self-reported compliance by employees.

Methods: A total of 360 companies had participated in the telephone survey (in October and November 2006) and were also visited by inspectors directly after the survey to establish compliance. The sampling frame included companies with 5 or more employees, stratified according to the number of employees and type of economic activity.