Search results for "bootstrap"
showing 10 items of 67 documents
A Plot-scale uncertainty analysis of saturated hydraulic conductivity of a clay soil
2021
Abstract Simulating soil hydrological processes at the plot or field scale requires using spatially representative values of the saturated soil hydraulic conductivity, Ks. Sampling campaigns should yield a reliable mean of Ks with a sustainable workload since measuring Ks at many points is challenging. Uncertainty analysis can be used to determine the lowest number of measurements that yield a mean Ks value with a specified accuracy level. Potential and limitations of this analysis were tested in this investigation for different extents of the sampled area and sampling densities. A clay soil was sampled intensively on two plots (plot area = 44 m2), two dates and using both small (0.15 m in …
Comparative biogeography of echinoids, bivalves and gastropods from the Southern Ocean.
2013
ABSTRACTAim Biogeographical patterns within three classes, the Echinoidea, Bivalvia andGastropoda, were investigated in Antarctic, sub-Antarctic and cold-temperateareas based on species occurrence data. Faunal similarities among regions wereanalysed to: (1) test the robustness of the biogeographical patterns previouslyidentified in bivalves and gastropods; (2) compare them with the biogeographi-cal patterns identified for echinoids; and (3) evaluate the reliability of the bio-geographical provinces previously proposed, depending on the taxa andtaxonomic levels analysed.Location The Southern Ocean, sub-Antarctic islands and cold-temperate areassouth of 45° S latitude at depths of < 1000 m.Meth…
The effects of data collection and observation methods on uncertainty of social networks in wild primates
2020
International audience; In social species, network centralities of group members shape social transmission and other social phenomena. Different factors have been found to influence the measurement of social networks, such as data collection and observation methods. In this study, we collected data on adults and juveniles and examined the effect of data collection method (ad libitum sampling vs. focal animal sampling) and observation method (interaction—grooming; play—vs. association—arm‐length; 2 m; 5 m proximities—) on social networks in wild vervet monkeys. First, we showed using a bootstrapping method, that uncertainty of ad libitum grooming and play matrices were lesser than uncertaint…
Associations between parental food choice motives, health-promoting feeding practices, and infants' fruit and vegetable intakes: the Food4toddlers st…
2020
Background: Parents influence their infants' diets and are the providers of healthy foods such as fruit and vegetables. Parental motives can influence infant's diets directly or through parental feeding practices. Objective: This study aimed to assess the associations between parental food choice motives and infants' fruit and vegetable intakes and to examine whether parental feeding practices mediated these associations. Design: A total of 298 parents participated in the Norwegian Food4toddlers study. Before the child's first birthday (mean age = 10.9 months), the parents completed an online baseline questionnaire. Five parental food choice motives were assessed: health, convenience, senso…
Pitfalls of hypothesis tests and model selection on bootstrap samples: Causes and consequences in biometrical applications
2015
The bootstrap method has become a widely used tool applied in diverse areas where results based on asymptotic theory are scarce. It can be applied, for example, for assessing the variance of a statistic, a quantile of interest or for significance testing by resampling from the null hypothesis. Recently, some approaches have been proposed in the biometrical field where hypothesis testing or model selection is performed on a bootstrap sample as if it were the original sample. P-values computed from bootstrap samples have been used, for example, in the statistics and bioinformatics literature for ranking genes with respect to their differential expression, for estimating the variability of p-v…
Optimal Cut Points for Remission and Response for the German Version of the Social Phobia Anxiety Inventory (SPAI).
2018
The German version of the Social Phobia and Anxiety Inventory (SPAI-G) is a validated measure for the detection of social anxiety disorder (SAD). The aim of the present study was to develop optimal cut points (OC) for remission and response to treatment for the SPAI-G.We used Receiver Operating Characteristic methods and bootstrapping to analyse the data of 359 patients after psychotherapeutic treatment. OCs where defined as the cut points with the highest sensitivity and specificity after bootstrapping.For remission, an OC of 2.79 was found, and for response, a change in score from pre- to posttreatment by 11% yielded best results.The OC we identified for remissionmay be used to improve th…
Interneta veikals
2016
“Interneta veikals” ir publiska tiešsaistes sistēma, kas sniedz iespēju lietotājam apskatīt produktus, atlasot tos pēc kategorijām, apskatīt produkta detalizēto informāciju, pievienot to grozam, reģistrēties, pieteikties sistēmā, pirkt produktus, apskatīt savu iepirkumu vēsturi un atcelt kādu no pasūtījumiem, ja tas ir nepieciešams. Vietnes administratoram ir iespēja veidot/labot/dzēst kategorijas un produktus, importēt produktus no MS Excel faila, kā arī apskatīt visu lietotāju pirkumus un mainīt statusu kādam no tiem.
Modelling the dynamics of the students’ academic performance in the German region of the North Rhine-Westphalia: an epidemiological approach with unc…
2013
Student academic underachievement is a concern of paramount importance in Europe, where around 15% of the students in the last high school courses do not achieve the minimum knowledge academic requirement. In this paper, we propose a model based on a system of differential equations to study the dynamics of the students academic performance in the German region of North Rhine-Westphalia. This approach is supported by the idea that both, good and bad study habits, are a mixture of personal decisions and influence of classmates. This model allows us to forecast the student academic performance by means of confidence intervals over the next few years.
Emergence of statistically validated financial intraday lead-lag relationships
2014
According to the leading models in modern finance, the presence of intraday lead-lag relationships between financial assets is negligible in efficient markets. With the advance of technology, however, markets have become more sophisticated. To determine whether this has resulted in an improved market efficiency, we investigate whether statistically significant lagged correlation relationships exist in financial markets. We introduce a numerical method to statistically validate links in correlation-based networks, and employ our method to study lagged correlation networks of equity returns in financial markets. Crucially, our statistical validation of lead-lag relationships accounts for mult…