One-way Random Effects Model Research Articles

Tolerance Intervals Under a Class of Unbalanced Linear Mixed Models

The study of tolerance intervals for linear mixed models under unbalanced data has been mainly focused on one-way random-effects models. In this article, we present a method to compute both one- and two-sided ( β , γ ) -tolerance intervals that is applicable to a more general class of unbalanced linear mixed models. The proposed method is based on the concept of generalized pivotal quantities and thus relies on the derivation of pivotal quantities that are shown to be independent within this particular class of models. The method employs Monte Carlo sampling methods to obtain realizations of the quantities needed to compute the tolerance intervals of interest. Extensive simulation studies confirm that coverage probabilities of the computed tolerance intervals are consistently close to their nominal levels. Furthermore, to showcase the application of our method in real-world scenarios, we provide illustrative examples of case studies that examine models falling within the specified class. Lastly, motivated by the prospective application of our method in drug development, we implement the proposed procedures to estimate shelf life of a drug product through tolerance intervals and unbalanced stability data.

The impact of COVID-19 on deaths from dementia and Alzheimer’s disease in Chile: an analysis of panel data for 16 regions, 2017–2022

Although several studies have documented the detrimental impacts of global COVID-19 containment measures on individuals with Alzheimer's disease and dementia, a comprehensive analysis of mortality rates for these conditions within the Chilean population is notably lacking. This study aimed to analyze the impact of COVID-19 on mortality rates among individuals with dementia and Alzheimer's disease in Chile. A retrospective longitudinal cross-sectional study was conducted, considering mortality data for specific mental health conditions during the pre-pandemic and pandemic contexts of COVID-19 in Chile. Quantile regression techniques were employed to analyze the existence of differences between the two periods, while non-observable heterogeneity models for panel data methods were used to evaluate the effect of COVID-19 mortality on crude mortality rates. Statistically significant differences were observed in the number of deaths from dementia and Alzheimer's disease between the pre-pandemic and COVID-19 pandemic periods. Specifically, crude mortality rates decreased by 10% (-0.10 [95% CI:-0.16,-0.05]) during the pandemic period. Furthermore, the number of deaths from COVID-19 during the pandemic period has a very weak incidence of deaths from mental health conditions such as dementia and Alzheimer's. Specifically, a unit percentage increase in confirmed cases from COVID-19 would result in a 7% (-0.07 [95% CI:-0.13,-0.001]) decrease in the number of deaths from dementia and Alzheimer's. These findings are supported by the application of panel regression with one-way random effects models. The study findings indicate a reduction in mortality rates attributed to dementia and Alzheimer's disease during the COVID-19 pandemic in Chile. This decline could be attributed to the potential underreporting of mental illness as the cause of death during the pandemic period. Several studies have highlighted that approximately 30% of death certificates fail to document the presence of a dementia syndrome. Moreover, the cause of death recorded for individuals with mental health conditions may be influenced by the physician's familiarity with the patient or reflect the prevailing approach to managing end-stage dementia patients. This work received no funding.

Investigating the Utility of Near-Infrared Reflectance Imaging for Diabetic Retinopathy Screening.

We investigated the reliability of near-infrared reflectance (NIR) imaging as a method of assessing severity of diabetic retinopathy (DR). One hundred ninety-five NIR images were reviewed by two graders for the number of hyporeflective foci, presence or absence of vascular abnormalities, and presumptive DR stage; these were correlated to fundus photography-defined DR stage. Interrater reliability was confirmed via one-way random effects model of intraclass correlation coefficients. Analysis of variance was used in subgroup analysis, receiver operating characteristic (ROC) curves were created to validate reliability of the model, and logistic regression was used to model foci and vascular abnormalities as predictors for moderate or worse disease. A statistically significant difference in mean number of hyporeflective foci was found between no DR and moderate non-proliferative DR (NPDR; P < 0.0001), no DR and severe NPDR (P < 0.001), no DR and proliferative DR (PDR; P < 0.0001), mild and moderate NPDR (P = 0.008), mild and severe NPDR (P < 0.001), and mild NPDR and PDR (P < 0.001). The area under the ROC curve was 0.849 (CI: 0.792 to 0.905). The threshold for detection of moderate NPDR or worse was 4.75 foci, with a sensitivity of 79.0% and a false positive rate of 20.0%. Multivariate logistic regression model incorporating hyporeflective foci with vascular abnormalities (odds ratio [OR] = 1.592, 95% CI: 1.381 to 1.835; P < 0.001) was able to accurately predict moderate disease or worse, just moderate disease (OR = 1.045, 95% CI: 1.003 to 1.089; P = 0.035), severe disease (OR = 1.050, 95% CI: 1.006 to 1.096; P = 0.027), and proliferative disease (OR = 1.050, 95% CI: 1.008 to 1.095; P = 0.018). NIR imaging may be an adjunct tool in screening for DR. [Ophthalmic Surg Lasers Imaging Retina 2024;55:XX-XX.].

A contribution to the French validation of the clinical anxiety scale amongst health care workers in Switzerland

BackgroundAnxiety disorders are frequent but remain often underdiagnosed and undertreated. Hence, valid screening instruments are needed to enhance the diagnostic process. The Clinical Anxiety Scale (CAS) is a 25-item anxiety screening tool derived from the Hamilton Anxiety Scale (HAM-A). However, this scale is not available in French. The General anxiety disorder − 7 (GAD-7) scale, which has been validated in French, is a 7-item instrument with good psychometric properties. This study contributes to the validation of an adapted French version of the CAS, using the GAD-7 as the reference.MethodsA forward-backward English-French-English translation of the CAS was performed according to standard practice. The French versions of the CAS and GAD-7 were completed by 127 French speaking healthcare professionals. CAS internal consistency was assessed using Crohnbach’s alpha, and test-retest reliability was tested after 15 days in a subsample of 30 subjects. Convergent validity with GAD-7 was assessed using Pearson’s correlation coefficient. Test-retest reliability was explored using one-way random effects model to calculate the intra-class correlation coefficient (ICC).ResultsFrench CAS showed excellent internal consistency (Cronbach’s alpha 0.97), high convergent validity with GAD-7 (Pearson’s R 0.81, p < 0.001), and very good test-retest reliability (ICC = 0.97, 95% CI 0.93–0.98).ConclusionThe proposed French version of the CAS showed high reliability and validity that need to be further investigated in different populations.

In-person validation of the Ichthyosis Scoring System.

Ichthyoses are a heterogeneous group of skin disorders characterized by scaling and erythema. Recognizing the variability of scale and erythema by region and ichthyosis subtype, we developed the Ichthyosis Scoring System (ISS) to quantify severity. We previously found ISS to have high inter- and intrarater reliability in evaluating photographic images. To confirm ISS clinical utility, we examined its performance at the 2022 Foundation for Ichthyosis and Related Skin Types conference. Sixty-five participants were evaluated by 3 of 9 medical professionals trained to score ichthyosis scale and erythema using ISS. Intrarater and interrater intraclass correlation coefficients (ICC) were analyzed using one-way and two-way random effects models, respectively. Intrarater reliability was excellent (ICC = 0.931, 95% CI, 0.921-0.940) for scale and good (ICC = 0.876, 95% CI, 0.853-0.899) for erythema scoring. Compared to photo validation with excellent intrarater reliability ratings for both scale (ICC = 0.956, 95% CI, 0.925-0.974) and erythema (ICC = 0.913, 95% CI, 0.855-0.949), ISS demonstrated equivalent reliability for live use. Overall interrater reliability for 10 body sites showed excellent (ICC >0.9) and good (ICC >0.75) agreement and consistency for both scale and erythema. Palms were an exception, demonstrating moderate (ICC >0.5) interrater agreement and consistency for erythema evaluation. ISS is a reliable measure of global and regional ichthyosis severity during in-person evaluations. Ease-of-use, accessibility, and content validity in both live and photographic evaluation endorse ISS as a standard for ichthyosis severity analysis.

Theoretical Study for Adjusting ANOVA Procedures For The One-Way Random Effects Model Under Correlated Errors Within Class And Across Classes

In this study, a method was developed to adjust the procedures of analysis of variance for the one-way balanced random effects model when error limits across classes are not independent, while the assumption of independence between the error terms among the different classes is essential in the analysis of variance. The variance-covariance structure and the correlation coefficients for the error limits were defined. The was assumed as the correlation coefficient of error terms within the class and the is the correlation coefficient for error terms in different classes. The work performed by deriving correction factor and calculating the expectation of the mean sum of squares of errors and treatments as well as correcting the f-statistic.

Bootstrap inference for skew-normal unbalanced heteroscedastic one-way classification random effects model

In this paper, the one-sided hypothesis testing and interval estimation problems for the fixed effect and variance component functions are considered in the skew-normal unbalanced heteroscedastic one-way classification random effects model. Firstly, the Bootstrap approach is used to establish test statistic for fixed effect. Secondly, the test statistics and confidence intervals for variance component functions are constructed by Bootstrap approach and generalized approach, and their theoretical properties are discussed. The Monte Carlo simulation results indicate that the Bootstrap approach performs better than the generalized approach in most cases. Finally, the above approaches are illustrated with two real examples of the annual average concentrations of fine particulate matter and nitrogen dioxide.

EVALUATING INTER-RATER RELIABILITY OF THE MODIFIED GORDON SCORE FOR PIN SITE INFECTION

There is no consensus on how to evaluate and grade pin site infection. A precise, objective and reliable pin site infectious score is warranted. The literature was reviewed for pin site infection classification systems, The Modified Gordon Score (MGS) grade 0-6 was used. The aim was to test the reliability of The Modified Gordon Infection Score. The observed agreement and inter-rater reliability were investigated between nurse and doctors.MGS was performed in the outpatient clinic at Aalborg University Hospital, Denmark on 1472 pin sites in 119 patients by one nurse and one of three orthopaedic surgeons blinded to each other's judgement. The data was stored in a Red Cap Database for further statistical analysis. The observed agreement between the nurse and the 3 orthopaedic surgeons was evaluated with a one-way random-effect model with interclass correlation with absolute agreement. Furthermore the observed agreement for each of the 3 surgeons with the nurse was calculated.The distribution of MGS infection grade in the 1472 pin sites was: Grade 0; n=1372, Grade 1; n=32, Grade 2; n=39, Grade 3; n=24, Grade 4; n=5, Grade 5; n=0, Grade 6; n=0.The observed agreement between the nurse and the surgeons was calculated as 98%. The ICC estimated between nurse and the surgeons was 0,8943 (ICC &gt;0,85 = reliable). The grading was done by three different doctors with an agreement with the nurse as follows. Rater1 (n=416) =99,5 %, Rater2 (n=1440) =97,4%, Rater3 (n=1440) =96,6%.A limitation to this study is that the dataset represents mostly clean pin sites with MGS 0. Only 100 pin sites had signs of superficial infection MGS 1-4 none above 4. We found that the MGS infection score is highly reliable for low grade infections but we cannot conclude on reliability in severe infections.

Self-reported musculoskeletal disorders questionnaire for agriculturists: An online self-assessment tool development.

The musculoskeletal disorders (MSDs) severity and frequency questionnaire (MSFQ) has been used with agriculturists. Although it frequently appears in the literature, it does not periodically reflect the levels of MSDs. This study aimed to develop a MSDs assessment tool for agriculturists via an online database. The four hospitals that were assigned to the development and tryout group received a random selection of participants from 33 health promoting hospitals. In the development phase, 55 agriculturists (from two hospitals) completed the structured interview questionnaire. The MSFQ document for the analysis of MSDs symptoms among agriculturists was concentrated on the frequency and severity of symptoms. The online MSFQ was checked by using intraclass correlation coefficients (ICC) in a one-way random-effects model. In the tryout phase, a group of 44 agriculturists (from another two hospitals) completed a similar online MSFQ. Cronbach's alpha was used to test the reliability of the online self-reported MSDs questionnaires. A Likert rating scale, used to measure the satisfaction of users, was divided into three categories: information, program design, and benefits. The development phase showed an ICC = 0.99 with a 95% CI = 0.98-0.99. More than 65 percent of agriculturists were female, aged from 41-50 years old. A large number of them were engaged in self-cultivation. Their main crops were rice and cassava. In total, 50% reported that they had experienced mild MSDs levels. The shoulder, knee-calf, and hip-thigh areas were the top three parts of the body where agriculturists had experienced MSDs from cultivation. Excellent reliability of online MSFQ was found after the tryout. The agriculturists were very satisfied overall (information, program design, and benefits). Developments to the MSFQ and online administration did not diminish its reliability for obtaining information about the level of MSDs of agriculturists' musculoskeletal symptoms. This self-reported MSDs questionnaire was appropriate to be used among agriculturists.

Utilizing a Population-Genetic Framework to Test for Gene-Environment Interactions between Zebrafish Behavior and Chemical Exposure.

Individuals within genetically diverse populations display broad susceptibility differences upon chemical exposures. Understanding the role of gene-environment interactions (GxE) in differential susceptibility to an expanding exposome is key to protecting public health. However, a chemical's potential to elicit GxE is often not considered during risk assessment. Previously, we've leveraged high-throughput zebrafish (Danio rerio) morphology screening data to reveal patterns of potential GxE effects. Here, using a population genetics framework, we apportioned variation in larval behavior and gene expression in three different PFHxA environments via mixed-effect modeling to assess significance of GxE term. We estimated the intraclass correlation (ICC) between full siblings from different families using one-way random-effects model. We found a significant GxE effect upon PFHxA exposure in larval behavior, and the ICC of behavioral responses in the PFHxA exposed population at the lower concentration was 43.7%, while that of the control population was 14.6%. Considering global gene expression data, a total of 3746 genes showed statistically significant GxE. By showing evidence that heritable genetics are directly affecting gene expression and behavioral susceptibility of individuals to PFHxA exposure, we demonstrate how standing genetic variation in a heterogeneous population such as ours can be leveraged to test for potential GxE.

Comparison of confidence intervals for variance components in an unbalanced one-way random effects model

Abstract The purpose of this paper is to study and compare the methods for constructing confidence intervals for variance components in an unbalanced one-way random effects model. The methods are based on a classical exact, generalised pivotal quantity, a fiducial inference and a fiducial generalised pivotal quantity. The comparison of criteria involves the empirical coverage probability that maintains at the nominal confidence level of 0.95 and the shortest average length of the confidence interval. The simulation results show that the method based on the generalised pivotal quantity and the fiducial inference perform very well in terms of both the empirical coverage probability and the average length of the confidence interval. The classical exact method performs well in some situations, while the fiducial generalised pivotal quantity performs well in a very unbalanced design. Therefore, the method based on the generalised pivotal quantity is recommended for all situations.

A32 DEVELOPMENT AND VALIDATION OF THE TORONTO UPPER GASTROINTESTINAL CLEANING SCORE

BackgroundHigh quality esophagogastroduodenoscopy (EGD) depends on the ability to appropriately visualize upper gastrointestinal (GI) mucosa pathology. Evaluation can be limited by the presence of mucus, foam, bubbles and solid materials. Currently, there is no standardized method to assess mucosal visualization for use in clinical or research settings.AimsTo develop and establish the content validity of the Toronto Upper Gastrointestinal Cleaning Score (TUGCS) and evaluate its interrater reliability.MethodsAn international panel of endoscopy experts rated potential items and their associated anchors for importance as indicators of adequacy of mucosal visualization during EGD. The survey utilized a Likert scale (1 (strongly disagree) to 5 (strongly agree)). The Delphi process was repeated until consensus was reached. Consensus was defined priori as ≥80% of experts in a given round scoring ≥4 on all survey items. To assess content validity, 48 EGD procedures were evaluated in real-time by two endoscopist reviewers using the TUGCS at a single institution. The interrater agreement between assessments was calculated for TUGCS total scores using intraclass correlation coefficient, one-way random effects model (ICC 1,1).ResultsFourteen experts agreed to be part of the Delphi panel. An anatomical framework representing the upper GI mucosa and anchors for each mucosal portion representing various levels of visibility was generated through systematic review. Three survey rounds, with response rates of 100%, 100% and 71% respectively, achieved consensus. The final TUGCS includes four anatomical areas (fundus, body, antrum, duodenum) and mucosal visualization anchors ranging from 0 to 3 (Figure 1). TUGCS was used to assess foregut cleaning in 48 procedures (Table 1). The mean TUGCS for staff and trainee were 8.1 (±2.4) and 8.1 (±2.6), respectively. The ICC was 0.78 (95% confidence interval 0.62–0.88) indicating good reliability.ConclusionsWe developed and generated content validity evidence for the TUGCS through rigorous Delphi methodology, reflective of practice across different centres. Planned as future research is a video survey distributed to endoscopists internationally to further validate the TUGCS to create a tool that may be used to judge mucosal visualization for EGD in research and clinical settings.Table 1. Patient Characteristics (n=48)Age, mean (±SD)55.4 (18.6)Sex, nMale20Female28Fasting duration (hours), mean (±SD)14.9 (10.5)Procedure typeElective47Acute1Figure 1. TUGCS toolFunding AgenciesNone

Impact of COVID-19 on deaths from respiratory diseases: Panel data evidence from Chile

ABSTRACT The COVID-19 pandemic has relegated pathologies that were previously commonplace to a secondary context. Therefore, it is necessary to study the evolution of these diseases in the presence or absence of COVID-19. Objective The present study had the following objectives: 1. to evaluate the relationship between the COVID-19 epidemic and the possible decrease in death from respiratory disease (DRd) in Chile; and 2. to study the relationships between meteorological variables and severity of COVID-19 with respect to DRd from January 2018 to February 2021. Methods The variable number of DRds in Chile was analyzed considering the monthly records of meteorological variables (temperature, precipitation and humidity) in each region of Chile and the severity of COVID-19 to evaluate the mortality trend before and after the pandemic. For this, different nonobservable heterogeneity models for panel data were used. Results The variables that affect DRd include the number of deaths from COVID-19, which led to a decrease in DRd (negative effect) when increased, the number of patients with COVID-19 in the intensive care unit (ICU), which led to an increase in DRd (positive effect) when increased, and the minimum temperature, which had a negative effect on DRd. These results are supported by the application of panel regression with one-way random-effects models. Conclusion This study revealed a reduction in the number of DRds other than COVID-19 during the pandemic in Chile. This could be explained by the sanitary measures applied by the Ministry of Health of Chile in relation to mobility restrictions and social distancing, among others. Therefore, DRd decreased in accordance with the appearance of the COVID-19 pandemic.

Upper Trapezius Muscle Tonicity, Assessed by Palpation, Relates to Change in Tissue Oxygenation and Structure as Measured byTime-Domain Near Infrared Spectroscopy.

Palpation is a diagnostic tool widely used by manual therapists despite its disputed reliability and validity. Previous studies have usually focused on the detection of myofascial trigger points (MTrPs), i.e., the points within muscles thought to have undergone molecular composition, oxygenation and structural changes, altering their tonicity. Time-domain near-infrared spectroscopy (TD-NIRS) could provide new insights into soft tissue oxygenation and structure, in order to objectively assess the validity and reliability of palpation. This pilot study aims at (1) assessing the ability of TD-NIRS to detect a difference between palpably normal and hypertonic upper trapezius (UT) muscles, and (2) to estimate the reproducibility of the TD-NIRS measurement on UT muscles. TD-NIRS measurements were performed on 4 points of the UT muscles in 18 healthy participants (10F, mean age: 27.6years), after a physical examination by a student osteopath to locate these points and identify the most and least hypertonic. From TD-NIRS, the most hypertonic points had a higher concentration in deoxy- ([HHb]) (0.887±0.253μM, p<0.001) and total haemoglobin ([HbT]) (1.447±0.772μM, p<0.001), a lower tissue oxygen saturation (StO2) (-0.575±0.286%, p<0.001), and a greater scattering amplitude factor (AF) (0.2238±0.1343 cm-1, p=0.001) than the least hypertonic points. Moreover, the intraclass correlation coefficient one-way random-effects model (ICC (1,1)) calculated for each TD-NIRS parameter and for each point revealed an excellent reliability of the measurement (Mean±SD, 0.9253±0.0678). These initial results, showing that changes in TD-NIRS parameters correlate with changes in muscle tonicity as assessed by palpation, are encouraging and show that TD-NIRS could help to further assess the validity of palpation as a diagnostic tool in manual therapy.

Skin Color Matters in the Latinx Community: A Call for Action in Research, Training, and Practice

While skin color is relevant and important in the Latinx community, as it is associated with colorism, little is known about how often it is measured or the best way to measure it. This article presents results from two studies examining these key concerns in three prominent journals, where Latinx research is typically published (i.e., the Hispanic Journal of Behavioral Sciences, the Journal of Latinx Psychology, and Cultural Diversity and Ethnic Minority Psychology). Study one examined whether skin color was measured as a variable, and if so, what measures and methodologies were used. A review of articles ( n = 1,137) showed few studies measured skin color in these three journals, with studies that did so relying on various approaches. Study two aimed to assess the reliability of a widely used skin color measure, the Massey-Martin scale, also known as the New Immigrant Survey (NIS) Skin Scale. Using a sample of 169 undergraduate students, self-ratings, coder ratings, and in vivo ratings were obtained and compared. One-way random effects model analyses indicated excellent reliability with minimal variability across the various ratings. Our findings suggest a critical need to engage in a more concerted effort to assess and discuss the relevance and importance of skin color within the Latinx community. The authors offer some suggestions on how to facilitate these efforts in clinical, training, and research arenas.

HOW BORSA ISTANBUL (BIST) REACTS TO THE NOVEL CORONAVIRUS: THE COVID-19 CASE

The purpose of this study is to investigate the response of the Turkish stock market to the novel coronavirus pandemic. To probe the issue, a dataset based on a total of 23 selected Borsa Istanbul (BIST) subindices of BIST Industrials, Services, and Financial indices for the period between 20 March, 2020 and 31 December, 2020 is utilized together with the growth in the weekly numbers of new COVID-19 cases and deaths both for Turkey and the world. A total of four models are run using panel data analysis on 943 index-date observations. The results of the One-way random effects models with time effects reveal that BIST indices react negatively to the growth in weekly COVID-19 new case and death numbers for both Turkey and the world. Further findings as to the control variables show that while Credit Default Swap (CDS) figures reduce selected stock index returns, Chicago Board Options Exchange Volatility Index figures known as Fear Index (VIX) are found to increase them during the observation period.

Accurate confidence intervals for inter-laboratory calibration and common mean estimation

For a calibration problem that arises in analytical chemistry, the Rocke-Lorenzato model and some generalizations are considered, so as to capture the near constant variability at very low levels of the analyte, and the increasing measurement variation with increased concentration of the analyte. For the common mean problem, a heteroscedastic one-way random effects model is often used to model the data and will be considered herein. Existing interval estimation procedures for these problems are likelihood based large sample procedures, and are not satisfactory, especially for small samples. A modified likelihood methodology, which can be numerically implemented, is shown to perform very well for the above problems. The analysis of inter-laboratory data is reported in order to illustrate the application of the proposed methods.

Development and validation of a postgraduate anaesthesiology core curriculum based on Entrustable Professional Activities: a Delphi study.

Background: Postgraduate training curricula should not be based on time-spans or predefined numbers of performed procedures. One approach to link competencies to clinical tasks is the concept of Entrustable Professional Activities (EPA). The goal of this study was the definition, ranking and validation of EPAs for anaesthesiology postgraduate training and the creation of an anaesthesiologic core curriculum. Methods: Anaesthesiologists of different levels of training participated in the study (single-center, cross-sectional) . First, an expert group defined a preliminary list of EPAs. Then a first Delphi round (n= 47 participants) was applied to identify daily anaesthesiology tasks with the goal to define EPAs. From the first Delphi round a new set of EPAs was defined, using the template and mapping method. Through an alignment process, conducted by the expert group, the preliminary EPAs and the new set of EPAs from the first Delphi round were summarised into a new list of EPAs. This list was presented to the study participants in a second Delphi round (n=80 participants), with the goal to validate and rank each EPA and to define the year of entrustment. For this purpose, participants were asked in the second Delphi round if each EPA should be included into an anaesthesiology core curriculum and in which year of training entrustment should take place. Furthermore, they were asked to rank each EPA on a numeric scale, defining its importance. From this numeric scale, the content validity index (CVI) for each EPA was calculated.Consensus of the results from the second Delphi round was calculated, using the one-way random effects model to calculate Intra-Class-Correlations (ICC). Percentages of agreement among the whole set of EPAs of this study and a previously published set of EPAs were computed.Results: A core-curriculum comprising of 39 EPAs was developed. The EPAs were subdivided into superior/high and inferior/low scoring EPAs, reflecting their importance and were mapped to the year of entrustment. The results reached high consensus among the different participating anaesthesiologist groups (overall agreement was 0.96 for the CVI of each EPA and 0.83 for the year in which the EPAs should be entrusted). Agreement with the previously defined set of EPAs was 73.3%.Conclusion: This study provides a further step in transforming postgraduate anaesthesiology training into a more contemporary approach. Other studies are necessary to complete and amend the presented core curriculum of EPA based postgraduate anaesthesiology training.

Estimation of bias-corrected intraclass correlation coefficient for unbalanced clustered studies with continuous outcomes

Intraclass correlation coefficient for data in a clustered study is traditionally estimated from a one-way random-effects model. This model assumes normality for the random cluster effect and the residual effect. When the normality assumption is questionable, we find that the estimated correlation could be much below the nominal level when data are highly skewed or data have low kurtosis. We develop a bias-corrected estimator based on the approach by Thomas and Hultquist for a study with unbalanced cluster sizes. For multivariate normal data or non-normal data with moderate skewness, we compare the performance of the new bias-corrected estimator with two existing estimators with regards to accuracy and precision. When correlation is small, the existing ANOVA estimator works well. When correlation is medium to large, the proposed new estimator has the correlation close to the nominal level, and its mean squared error is smaller than others.

Improved $U$-tests for variance components in one-way random effects models

Based on a decomposition of a $U$-statistic, Nobre, Singer and Silvapulle (In Beyond Parametrics in Interdisciplinary Research, Festschrift to P.K. Sen (2008) 197–210 Institute of Mathematical Statistics) proposed a test for the hypothesis that the within-treatment variance component in a one-way random effects model is null, specially useful when very mild assumptions are imposed on the underlying distributions. We consider a bootstrap version of that $U$-test and evaluate its performance via simulation studies in different scenarios. The bootstrap $U$-test has better statistical properties than the original test even in small samples. Furthermore, it is easy to implement and has a low computational cost. We consider two examples with unbalanced small sample datasets, for illustrative purposes.