Confidence Intervals for Cronbach's Coefficient Alpha Values

Coefficient Alpha, which is widely used in empirical research, estimates the reliability of a test consisting of parallel items. In practice it is difficult to compare values of alpha across studies as it depends on the number of items used. In this paper we provide a simple solution, which amounts to computing the confidence intervals of an alpha, as these intervals automatically account for differences across the numbers of items. We also give appropriate statistics to test for significant differences of alpha values across studies

Did the incidence of high precipitation levels increase? Statistical evidence for the Netherlands

One of the possible consequences of global warming is that there will be more precipitation days throughout the year, and also that the level of precipitation will be higher. In this paper we provide a detailed statistical analysis of a century of daily precipitation levels for the Netherlands. We show that the often-considered gamma distribution does not fit well to the data. We argue that its incorrect use can lead to spuriously high probabilities of extreme precipitation levels. Relying on advanced nonparametric techniques, we first find that there is indeed more precipitation in the Netherlands, but that this involves only low levels, and second, that the probability of extremely high levels has not changed over time

Arthroscopic Meniscus Repair: Clinical and Isokinetic Results

The importance of the menisci for transmitting workloads in the knee joint to protect the articular cartilage is widely acknowledged. Therefore various techniques have been introduced to repair the damaged meniscus

Confidence intervals for maximal reliability of probability judgments

Subjective probabilities play an important role in marketing research, for example where individuals rate the likelihood that they will purchase a new to develop product. The tau-equivalent model can describe the joint behaviour of multiple test items measuring the same subjective probability. It improves the reliability of the subjective probability estimate by using a weighted sum as the outcome of the test rather than an unweighted sum. One can choose the weights to obtain maximal reliability. In this paper we stress the use of confidence intervals to assess maximal reliability, as this allows for a more critical assessment of the items as measurement instruments. Furthermore, two new confidence intervals for the maximal reliability are derived and compared to intervals derived earlier in \\citet{YuanBentler2002, RaykovPenev2006}. The comparison involves coverage curves, a methodology that is new in the field of reliability. The existing Yuan-Bentler and Raykov-Penev intervals are shown to overestimate the maximal reliability, whereas one of our proposed intervals, the stable interval, performs very well. This stable interval hardly shows any bias, and has a coverage for the true value which is approximately equal to the confidence level

Analyzing preferences ranking when there are too many alternatives.

Consumer preferences can be measured by rankings of alternatives. When there are too many alternatives, this consumer task becomes complex. One option is to have consumers rank only a subset of the available alternatives. This has an impact on subsequent statistical analysis, as now a large amount of ties is observed. We propose a simple methodology to perform proper statistical analysis in this case. It also allows to test whether (parts of the) rankings are random or not. An illustration shows its ease of application

Ranking Models in Conjoint Analysis

In this paper we consider the estimation of probabilistic ranking models in the context of conjoint experiments. By using approximate rather than exact ranking probabilities, we do not need to compute high-dimensional integrals. We extend the approximation technique proposed by \\citet{Henery1981} in the Thurstone-Mosteller-Daniels model for any Thurstone order statistics model and we show that our approach allows for a unified approach. Moreover, our approach also allows for the analysis of any partial ranking. Partial rankings are essential in practical conjoint analysis to collect data efficiently to relieve respondents' task burden

Molluscum contagiosum in Dutch general practice

BACKGROUND: While molluscum contagiosum is considered to be a frequently encountered disease, few data on its incidence are known. AIM: The objective of this study was to describe the incidence of molluscum contagiosum in Dutch general practice and to assess the importance of venereal molluscum contagiosum. METHOD: Data were taken from the national survey of morbidity and interventions in general practice, drawn from 103 practices across the Netherlands, with a study population of 332300. RESULTS: The infection appeared to be common in childhood (cumulative incidence 17% in those aged under 15 years); the adult, sexually transmitted, form was rare. Incidence was higher between January and June than between July and December. Cases were unequally divided between recording practices, which is though to have been caused by the occurrence of small epidemics. CONCLUSION: The incidence of molluscum contagiosum in Dutch general practice was found to be 2.4 per 1000 person years. Molluscum contagiosum should still be considered as a mainly paediatric disease

A New Type of Metal Recognition by Human T Cells: Contact Residues for Peptide-independent Bridging of T Cell Receptor and Major Histocompatibility Complex by Nickel

In spite of high frequencies of metal allergies, the structural basis for major histocompatibility complex (MHC)-restricted metal recognition is among the unanswered questions in the field of T cell activation. For the human T cell clone SE9, we have identified potential Ni contact sites in the T cell receptor (TCR) and the restricting human histocompatibility leukocyte antigen (HLA)-DR structure. The specificity of this HLA-DR–promiscuous VA22/VB17+ TCR is primarily harbored in its α chain. Ni reactivity is neither dependent on protein processing in antigen-presenting cells nor affected by the nature of HLA-DR–associated peptides. However, SE9 activation by Ni crucially depends on Tyr29 in CDR1α, an N-nucleotide–encoded Tyr94 in CDR3α, and a conserved His81 in the HLA-DR β chain. These data indicate that labile, nonactivating complexes between the SE9 TCR and most HLA-DR/peptide conjugates might supply sterically optimized coordination sites for Ni ions, three of which were identified in this study. In such complexes Ni may effectively bridge the TCR α chain to His81 of most DR molecules. Thus, in analogy to superantigens, Ni may directly link TCR and MHC in a peptide-independent manner. However, unlike superantigens, Ni requires idiotypic, i.e., CDR3α-determined TCR amino acids. This new type of TCR–MHC linkage might explain the high frequency of Ni-reactive T cells in the human population

A Microfluidic-Based Tyrosine Kinase and Phosphatase Assay

Background: Inappropriate prescribing is a well-known clinical problem in nursing home residents, but few interventions have focused on reducing inappropriate medication use. Objective: To examine successful discontinuation of inappropriate medication use and to improve prescribing in nursing home residents. Design: Pragmatic cluster randomized controlled trial, with clustering by elder care physicians and their wards. Setting: 59 Dutch nursing home wards for long-term care. Patients: Residents with a life expectancy greater than 4 weeks who consented to treatment with medication. Intervention: Multidisciplinary Multistep Medication Review (3MR) consisting of an assessment of the patient perspective, medical history, critical appraisal of medications, a meeting between the treating elder care physician and the pharmacist, and implementation of medication changes. Measurements: Successful discontinuation of use of at least 1 inappropriate drug (that is, without relapse or severe withdrawal symptoms) and clinical outcomes (neuropsychiatric symptoms, cognitive function, and quality of life) after 4 months of follow-up. Results: Nineteen elder care physicians (33 wards) performed the 3MR, and 16 elder care physicians (26 wards) followed standard procedures. A total of 426 nursing home residents (233 in the intervention group and 193 in the control group) were followed for an average of 144 days (SD, 21). In an analysis of all participants, use of at least 1 inappropriate medication was successfully discontinued for 91 (39.1%) residents in the intervention group versus 57 (29.5%) in the control group (adjusted relative risk, 1.37 [95% CI, 1.02 to 1.75]). Clinical outcomes did not deteriorate between baseline and follow-up. Limitations: The 3MR was done only once. Some withdrawal symptoms or relapses may have been missed. Conclusion: The 3MR is effective in discontinuing inappropriate medication use in frail nursing home residents without a decline in their well-being. Primary Funding Source: Netherlands Organisation for Health Research and Development

OPTIMAL VELOCITY PROFILES FOR VAULT

The aim of this study was to determine which kinematic characteristics may be used as a performance indicator(s) for vault. Over 600 vaults (299 men and 216 Women, see Table 1) were recorded and analyzed using footage of 3 high-speed cameras taken at the 2010 Rotterdam Artistic Gymnastics World Championships. The kinematics were correlated with the judge’s outcome score: type of vault, difficulty and final score. The correlation coefficients between velocity at takeoff and final judges’ scores were r = 0.60 for men and r = 0.52 for women