Search results for "Sample Size"
showing 10 items of 219 documents
Non-response bias as a likely cause of the association between young maternal age at the time of delivery and the risk of cancer in the offspring.
2003
Some epidemiological studies have shown an association between young maternal age at the time of delivery and risk of cancer in the offspring. In a recent German case-control study, there was a twofold increase in the leukaemia risk for children whose mothers were aged < 20 years at the time of delivery. As the prevalence of younger mothers among control families was particularly low, data on maternal age distributions for the general population of Germany were obtained in order to examine the representativeness of the control sample. Despite the excellent sampling frame based on data from complete and up-to-date population registries and a satisfactory response rate among controls ( approx…
Occupational exposure to extremely low frequency electric and magnetic fields and Alzheimer disease: a meta-analysis
2008
Background Among potential environmental risk factors for Alzheimer disease (AD), occupational exposures have received some attention, including extremely low frequency electromagnetic fields (ELF-EMF). A systematic review and meta-analysis of published epidemiological studies on this subject was carried out. Methods The search was concluded in April 2006. Bibliographic databases consulted included PubMed, EMBASE, Cochrane Library and NIOSHTIC2. Pooled estimates were obtained using random-effects meta-analysis. Sources of heterogeneity between studies were explored, as was publication bias. Results Fourteen different studies (nine case-control and five cohort studies) accomplished inclusion…
Revista electrónica de investigación y evaluación educativa
2014
Resumen basado en el de la publicación Título, resumen y palabras clave en inglés y español Se analiza el estatus del género existente en los equipos o consejos editoriales de las revistas científicas españolas de Educación. A priori, se indaga el estatus de la eminencia científica en el campo de la Educación; con el fin de detectar los posibles sesgos de género. Como análisis complementario se considera la nacionalidad o procedencia de los miembros de los consejos editoriales de las revistas de Educación. El hallazgo principal testimonia un fuerte sesgo contra las mujeres cuando éstas son consideradas editoras. Valencia ESP
Statistical validation of simulation models of observable systems
2003
In this paper, for validating computer simulation models of real, observable systems, an uniformly most powerful invariant (UMPI) test is developed from the generalized maximum likelihood ratio (GMLR). This test can be considered as a result of a new approach to solving the Behrens‐Fisher problem when covariance matrices of two multivariate normal populations (compared with respect to their means) are different and unknown. The test is based on invariant statistic whose distribution, under the null hypothesis, does not depend on the unknown (nuisance) parameters. The sample size and threshold of the UMPI test are determined from minimization of the weighted sum of the model builder's risk a…
Food selectivity in autism spectrum disorders: a systematic review.
2013
Autism spectrum disorders are characterized by difficulties with reciprocal social interactions and restricted patterns of behavior and interest; one of these characteristic behaviors is food selectivity. The objective of this study was to perform a systematic review of the literature published between 1970 and 2013 concerning this eating behavior. The articles identified were analyzed in terms of sample size, study design, and criteria for assessment and intervention, as well as the results, level of evidence and grade of recommendation. The main search was conducted in Medline, Cochrane Library, Scielo, ScienceDirect, and Embase). There is empirical evidence and an overall scientific con…
Meta-analysis of the relationship between teachers’ self-efficacy and attitudes toward inclusive education
2022
Abstract This meta-study aims to examine the size of the relationship between teachers' self-efficacy and attitudes toward inclusive education of K-12 students with special educational needs and to identify potential moderators (publication, sample, and research procedure characteristics). We synthesized the research conducted from 1994 to 2018, and 41 studies were included. Bare-bones meta-analysis with random effect model revealed a sample size weighted correlation coefficient between teachers’ self-efficacy and attitudes as r ¯ = 0.35 (CI = 0.31-0.39). The between-study variations were not associated with hypothesized publication and sample characteristics. However, the self-efficacy me…
Percentile Reference Charts for Selected Sleep Parameters for 20- to 80-Year-Old Healthy Subjects from the SIESTA Database. Referenzkurven fur ausgew…
2005
One of the aims of the SIESTA project was to establish a normative database of sleep parameters for healthy and sleep-disturbed patients. Reference data for sleep parameters in non-sleep-disturbed subjects are scarce and usually refer to means and standard deviations. However, since most of the parameters do not follow a Gaussian distribution, percentiles of the distribution provide more detailed information. The present results are based on data from 198 healthy, non-sleep-disturbed subjects (104 females) in the age range of 20 to 95 years. For every subject, two consecutive nights were polysomnographically recorded in one of the eight participating clinical centres. Percentile charts were…
I-states-as-objects-analysis (ISOA): Extensions of an approach to studying short-term developmental processes by analyzing typical patterns
2012
I-states-as-objects-analysis (ISOA) is a person-oriented methodology for studying short-term developmental stability and change in patterns of variable values. ISOA is based on longitudinal data with the same set of variables measured at all measurement occasions. A key concept is the i-state, defined as a person’s pattern of variable values at a specific time point. All i-states are first subjected to a classification analysis that results in a time-invariant classification characterized by a number of typical i-states. Each person is then characterized at each time point by the typical i-state he/she belongs to. Then the person’s sequences of typical i-states are analyzed with regard to …
Manual packing and soil reuse effects on determination of saturated hydraulic conductivity of a loam soil
2022
Abstract Performing laboratory measurement of saturated hydraulic conductivity, Ks, of sieved soil is important for many scientific purposes such as testing theories and methods to determine Ks. A given soil mass can be used only once or it can be reused after a previous use. Little is known on the dependence of the Ks measurements on both the applied packing method and the reuse of the same soil mass. This lack of knowledge makes comparisons among different investigations more or less uncertain. Four packing methods were tested on an initially dry loam soil by measuring Ks with the simplified falling head (SFH) technique. The four methods differed by the used compacting procedure (dropping…
Statistical analysis of latency outcomes in behavioral experiments
2011
In experimental designs of animal models, memory is often assessed by the time for a performance measure to occur (latency). Depending on the cognitive test, this may be the time it takes an animal to escape to a hidden platform (water maze), an escape tunnel (Barnes maze) or to enter a dark component (passive avoidance test). Latency outcomes are usually statistically analyzed using ANOVAs. Besides strong distributional assumptions, ANOVA cannot properly deal with animals not showing the performance measure within the trial time, potentially causing biased and misleading results. We propose an alternative approach for statistical analyses of latency outcomes. These analyses have less distr…