Search results for "Sample Size"
showing 10 items of 219 documents
A New Multinomial Accuracy Measure for Polling Bias
2014
In this article, we propose a polling accuracy measure for multi-party elections based on a generalization of Martin, Traugott, and Kennedy's two-party predictive accuracy index. Treating polls as random samples of a voting population, we first estimate an intercept only multinomial logit model to provide proportionate odds measures of each party's share of the vote, and thereby both unweighted and weighted averages of these values as a summary index for poll accuracy. We then propose measures for significance testing, and run a series of simulations to assess possible bias from the resulting folded normal distribution across different sample sizes, finding that bias is small even for polls…
Effect of the abundance of three predominating copepod species on adequate sample volume and sample size in Bransfield Strait (Antarctic Peninsula) a…
1992
The effect on adequate sample size and sample volume of the abundances of three predominant copepod species, Metridia gerlachei, Calanus propinquus and Calanoides acutus, were studied in Bransfield Strait (Antarctic Peninsula) in the austral summer of 1988–1989 and waters north of the Weddell Sea in 1989–1990. Copepod abundances were higher in the area north of the Weddell Sea, with the exception of Metridia gerlachei, which was evenly distributed over both areas. Local (intra-station) patchiness was not found, indicating random distribution over small areas. In the assessment of inter-station variability in Bransfield Strait, with standard error of the mean set arbitrarily at 20% of the av…
Sample allocation for efficient model-based small area estimation
2017
We present research results on sample allocations for efficient model-based small area estimation in cases where the areas of interest coincide with the strata. Although model-assisted and model-based estimation methods are common in the production of small area statistics, utilization of the underlying model and estimation method are rarely included in the sample area allocation scheme. Therefore, we have developed a new model-based allocation named g1-allocation. For comparison, one recently developed model-assisted allocation is presented. These two allocations are based on an adjusted measure of homogeneity which is computed using an auxiliary variable and is an approximation of the int…
The measurement invariance of Job Diagnostic Survey (JDS) across three university student groups
2016
Purpose: The main purpose of this study is to apply a multigroup confirmatory analysis to examine the measurement invariance (MI) of the adapted version of the Job Diagnosis Survey (JDS) as a measurement tool that analyses the relationship between the features of teaching methodologies with university students’ motivation and satisfaction across data collected on different degrees and academic years. Design/methodology/approach: Confirmatory factor analysis was carried out using a multigroup structural equation model, using the program EQS 6.1 to test the invariance of the adapted version of JDS in a sample constituted by 535 student of a Spanish public university. The assessment of invaria…
Prevalence of Catatonia and Its Moderators in Clinical Samples: Results from a Meta-analysis and Meta-regression Analysis
2017
Catatonia is an independent syndrome that co-occurs with several mental and medical conditions. We performed a systematic literature review in PubMed/Scopus until February 2017 and meta-analyzed studies reporting catatonia prevalence. Across 74 studies (cross-sectional = 32, longitudinal = 26, retrospective = 16) providing data collected from 1935 to 2017 across all continents, mean catatonia prevalence was 9.0% (k = 80, n = 110 764; 95% CI = 6.9-11.7, I2 = 98%, publication bias P < .01), decreasing to 7.8% (k = 19, n = 7612, 95% CI = 7-8.7, I2 = 38.9%) in a subgroup with low heterogeneity. Catatonia prevalence was 23.9% (k = 8, n = 1168, 95% CI = 10-46.9, I2 = 96%) in patients undergoin…
Update on the effects of graded motor imagery and mirror therapy on complex regional pain syndrome type 1: A systematic review.
2017
Graded motor imagery (GMI) and mirror therapy (MT) is thought to improve pain in patients with complex regional pain syndrome (CRPS) types 1 and 2. However, the evidence is limited and analysis are not independent between types of CRPS. The purpose of this review was to analyze the effects of GMI and MT on pain in independent groups of patients with CRPS types 1 and 2. Searches for literature published between 1990 and 2016 were conducted in databases. Randomized controlled trials that compared GMI or MT with other treatments for CRPS types 1 and 2 were included. Six articles met the inclusion criteria and were classified from moderate to high quality. The total sample was composed of 171 p…
Accuracy of pre-hospital triage tools for major trauma: a systematic review with meta-analysis and net clinical benefit
2021
Abstract Background We conducted a systematic review to evaluate and compare the accuracy of pre-hospital triage tools for major trauma in the context of the development of the Italian National Institute of Health guidelines on major trauma integrated management. Methods PubMed, Embase, and CENTRAL were searched up to November 2019 for studies investigating pre-hospital triage tools. The ROC (receiver operating characteristics) curve and net clinical benefit for all selected triage tools were performed. Quality assessment was performed using the Quality Assessment of Diagnostic Accuracy Studies–2. Certainty of the evidence was judged with the Grading of Recommendations Assessment, Developme…
Calculating confidence intervals for impact numbers
2006
Abstract Background Standard effect measures such as risk difference and attributable risk are frequently used in epidemiological studies and public health research to describe the effect of exposures. Recently, so-called impact numbers have been proposed, which express the population impact of exposures in form of specific person or case numbers. To describe estimation uncertainty, it is necessary to calculate confidence intervals for these new effect measures. In this paper, we present methods to calculate confidence intervals for the new impact numbers in the situation of cohort studies. Methods Beside the exposure impact number (EIN), which is equivalent to the well-known number needed …
Calculation of NNTs in RCTs with time-to-event outcomes: A literature review
2008
Abstract Background The number needed to treat (NNT) is a well-known effect measure for reporting the results of clinical trials. In the case of time-to-event outcomes, the calculation of NNTs is more difficult than in the case of binary data. The frequency of using NNTs to report results of randomised controlled trials (RCT) investigating time-to-event outcomes and the adequacy of the applied calculation methods are unknown. Methods We searched in PubMed for RCTs with parallel group design and individual randomisation, published in four frequently cited journals between 2003 and 2005. We evaluated the type of outcome, the frequency of reporting NNTs with corresponding confidence intervals,…
Comparing medical treatments for Crohn’s disease
2013
The drugs available for inflammatory bowel disease are aminosalicylates, antibiotics, steroids, immunosuppressors and biologics. The effectiveness of these drugs has been evaluated in many randomized clinical trials, mainly versus placebo. Few studies have been conducted comparing the different drugs among themselves, owing to the methodological problems raised by comparative trials, such as sample size and blindness. This review focuses mainly on the randomized clinical trials that have compared different treatments. Of course comparisons are mainly between drugs used in a particular setting (mild, moderate and severe disease). However, on many occasions there is no homogeneity in these cl…