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Spurious Heavy Tails / Falska tunga svansarSegerfors, Ted January 2015 (has links)
Since the financial crisis which started in 2007, the risk awareness in the financial sector is greater than ever. Financial institutions such as banks and insurance companies are heavily regulated in order to create a harmonic and resilient global economic environment. Sufficiently large capital buffers may protect institutions from bankruptcy due to some adverse financial events leading to an undesirable outcome for the company. In many regulatory frameworks, the institutions are obliged to estimate high quantiles of their loss distributions. This is relatively unproblematic when large samples of relevant historical data are available. Serious statistical problems appear when only small samples of relevant data are available. One possible solution would be to pool two or more samples that appear to have the same distribution, in order to create a larger sample. This thesis identifies the advantages and risks of pooling of small samples. For some mixtures of normally distributed samples, with what is considered to be the same variances, the pooled data may indicate heavy tails. Since a finite mixture of normally distributed samples has light tails, this is an example of spurious heavy tails. Even though two samples may appear to have the same distribution function it is not necessarily better to pool the samples in order to obtain a larger sample size with the aim of more accurate quantile estimation. For two normally distributed samples of sizes m and n and standard deviations s and v, we find that when v=s is approximately 2, n+m is less than 100 and m=(m+n) is approximately 0.75, then there is a considerable risk of believing that the two samples have equal variance and that the pooled sample has heavy tails. / Efter den finansiella krisen som hade sin start 2007 har riskmedvetenheten inom den finansiella sektorn ökat. Finansiella institutioner så som banker och försäkringsbolag är noga reglerade och kontrollerade för att skapa en stark och stabil världsekonomi. Genom att banker och försäkringsbolag enligt regelverken måste ha kapitalbuffertar som ska skydda mot konkurser vid oväntade och oönskade händelser skapas en mer harmonisk finansiell marknad. Dessa regelverk som institutionerna måste följa innebär ofta att de ansvariga måste skatta höga kvantiler av institutionens förväntade förlustfunktion. Att skapa en pålitligt modell och sedan skatta höga kvantiler är lätt när det finns mycket relevant data tillgänglig. När det inte finns tillr äckligt med historisk data uppkommer statistiska problem. En lösning på problemet är att poola två eller _era grupper av data som ser ut att komma från samma fördelningsfunktion för att på så sätt skapa en större grupp med historisk data tillgänglig. Detta arbetet går igenom fördelar och risker med att poola data när det inte finns tillräckligt med relevant historisk data för att skapa en pålitlig modell. En viss mix av normalfördelade datagrupper som ser ut att ha samma varians kan uppfattas att komma från tungsvansade fördelningar. Eftersom normalfördelningen inte är en tungsvansad fördelning kan denna missuppfattning skapa problem, detta är ett exempel på falska tunga svansar. Även fast två datagrupper ser ut att komma från samma fördelningsfunktion så är det inte nödvändigtvis bättre att poola dessa grupper för att skapa ett större urval. För två normalfördelade datagrupper med storlekarna m och n och standardavvikelserna s och v, är det farligaste scenariot när v=s är ungefär 2, n+m är mindre än 100 och m=(m+n)är ungefär 0.75. När detta inträffar finns det en signifikant risk att de två datagrupperna ser ut att komma från samma fördelningsfunktion och att den poolade datan innehar tungsvansade egenskaper.
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Density Functional Theory Study of Vibrational Spectra. 4. Comparison of Experimental and Calculated Frequencies of All-Trans-1,3,5,7-Octatetraene - the End of Normal Coordinate Analysis?Zhou, Xuefeng, Mole, Susan J., Liu, Ruifeng 01 January 1996 (has links)
Comparison of the observed and calculated vibrational frequencies of all-trans-octatetraene indicates that the density functional theory (DFT) using Becke's exchange and Lee-Yang-Parr's correlation functionals is as accurate as the Hartree-Fock (HF)-based scaled quantum mechanical force field approach in predicting fundamental vibrational frequencies. As the DFT calculation does not use any empirical parameters pertaining to the subject molecule and its computational cost scales more favorably than that of the HF theory, it is a more promising approach to molecular vibrational problems and should replace the empirical normal coordinate analysis for assisting vibrational assignments.
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Recognition Performance of Interrupted Monosyllabic Words: The Effects of Ten Interruption LocationsWilson, Richard H., Hamm, Heather M. 01 January 2015 (has links)
Background: A previous experiment with 70 interrupted monosyllabic words demonstrated that recognition performance was influenced by the location of an interruption pattern (Wilson, 2014). The interruption paradigm (10 interruptions/sec, 50% duty cycle periodic interruption) was referenced to word onset. The words were interrupted such that alternate 50-msec segments were parsed to separate files. In the 0-msec condition the first on-segment coincided with the word onset, whereas in the 50-msec condition the first on-segment occurred 50 msec after word onset. The 0- and 50-msec conditions were complementary halves. Recognition performance by young listeners was 19% better on the 0-msec condition (86%) than on the 50-msec condition (68%); there were a minority number of words on which the results were just the opposite. A second study using the same interruption paradigm but 300 different words reported similar relations, with 63% correct recognition on the 0-msec condition and 48% on the 50-msec condition (Wilson and Irish, 2015). Both studies suggest the importance that the first 50 msec of the target word has on intelligibility. Purpose: To define in detail the effects that interruption patterns have on word recognition as the interruption pattern was incremented with reference to word onset from 0 to 90 msec in 10-msec steps. Research Design: A repeated-measures design with ten interruption patterns (onset conditions). Study Sample: Twenty-four young listeners (19-29 yr) with normal hearing for pure tones participated in this study. Data Collection and Analyses: Seventy consonant-nucleus-consonant words formed the corpus of materials with 25 additional words used for practice. For each participant, the 700 stimuli (70 words by ten onset conditions) were interrupted (10 interruptions/sec; 50% duty cycle), randomized, and recorded on compact disc in 28, 25-word tracks. Results: The overall mean recognition performance was 80.4% with mean performances for the ten conditions ranging from 73.0% (50-msec condition) to 87.7% (90-msec condition). The mean recognition performances changed systematically, decreasing from the 0-msec condition to the 50-msec condition and then increasing to the 90-msec condition, which formed a U-shaped function of the means. Of the 45 mean paired comparisons (post hoc t-tests with Bonferroni corrections), there were 17 significant differences at the p ≤ 0.001 level, increasing to 31 significant differences when the significance level was increased to the p ≤ 0.01 level. Visual inspection of the 70-word performance functions revealed that 32 words had flat functions, 34 words had U-shaped functions, two functions were rising, one was an inverted V-shape, and one was irregular. Conclusions: First, some words (utterances of those words) were immune to any differential effects of the ten interruption patterns. These words with flat performance functions constituted 46% of the word corpus. Second, 49% of the words exhibited U-shaped performance functions that were always systematic, going from maximum to minimum and back to maximum. These words were thought to be more dependent on the initial consonant to attain maximum performance. The conclusion is that some words are not affected by the location of the interruption pattern (those with flat functions) whereas other words are substantially affected (those with U-shaped functions).
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Receipt of a False Positive Test Result During Routine Screening for Ovarian Cancer: A Teachable Moment?Floyd, Andrea, Steffens, Rachel F., Pavlik, Edward, Andrykowski, Michael A. 01 March 2011 (has links)
The term "teachable moment" (TM) has been used to describe a life transition or event which motivates an individual to change a behavior or presents an opportunity to intervene to prompt behavior change. We examined whether receipt of a false positive ovarian cancer (OC) screening result may represent a TM. 403 women participating in an OC screening program completed questionnaires assessing demographic, clinical, behavioral, and psychosocial information. The TM was operationalized as expressed interest in receiving health-related information. We hypothesized that among women receiving a false positive screening test result, those women who had experienced greater personal perceived risk for OC as well as distress would be more interested in receiving health-related information than women receiving a normal result. Analyses revealed that women receiving a false positive screening result were less interested in receiving health-related information than women receiving a normal screening result. For women receiving a false positive result, expressed interest in receipt of health-related information was only modestly related to distress and related even less to perceptions of OC risk. Our data do not support viewing a false positive OC screening result as a TM. Potential explanations for the current findings as well as recommendations for future research investigating the TM are discussed.
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An Introduction to Functional Independency in Relational Database NormalizationChen, Tennyson X., Liu, Sean Shuangquan, Meyer, Martin D., Gotterbarn, Don 17 May 2007 (has links)
In this paper, we discuss the deficiencies of normal form definitions based on Functional Dependency and introduce a new normal form concept based on Functional Independency. Functional Independency has not been systematically investigated while there is a very strong theoretical foundation for the study of Functional Dependency in relational database normalization. This paper will demonstrate that considering Functional Dependency alone cannot eliminate some common data anomalies and the normalization process can yield better database designs with the addition of Functional Independency.
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Idiopathic Polymorphic Ventricular Tachycardia With Normal QT Interval in a Structurally Normal HeartMechleb, Bassam, Haddadin, Tariq Z., Iskandar, Said B., Abboud, Lucien N., Fahrig, Stephen A. 01 July 2006 (has links)
Polymorphic ventricular tachycardia (PVT) is a life-threatening arrhythmia that is typically related to long QT syndrome, organic heart disease, electrolyte abnormalities, cardiotoxic drugs, or adrenergic stimulation. A review of the literature reveals that PVT with normal QT interval and without underlying cause is quite rare. We report a case of idiopathic spontaneous PVT with structurally normal heart and without electrolyte abnormalities, drug reactions, or evidence of catecholamine induced arrhythmia. We also review the literature on the electrocardiographic characteristics and management of idiopathic PVT.
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Peri-Procedural Aggressive Hydration for Post Endoscopic Retrograde Cholangiopancreatography (ERCP) Pancreatitis Prophylaxsis: Meta-analysis of Randomized Controlled TrialsRadadiya, Dhruvil, Devani, Kalpit, Arora, Sumant, Charilaou, Paris, Brahmbhatt, Bhaumik, Young, Mark, Reddy, Chakradhar 01 September 2019 (has links)
Background: Periprocedural intravenous hydration is suggested to decrease the risk of post-ERCP pancreatitis (PEP). However, quality of evidence supporting this suggestion remains poor. Here we hypothesized that aggressive hydration(AH) could be an effective preventive measure. Methods: Pubmed, EMBASE, CINAHL, Google Scholar, Clinical Trials. gov, Clinical Key, International Standard Randomized Trial Number registry as well as secondary sources were searched through January 2019 to identify randomized controlled studies comparing AH to standard hydration (SH) for prevention of PEP. Pooled odds ratio (OR) and 95% confidence intervals (CIs) were calculated using the random-effects model. RevMan 5.3 was used for analysis. Results: A total of 9 RCTs, with 2094 patients, were included in the meta-analysis. AH reduced incidence of PEP by 56% compared to SH (OR = 0.44, CI:0.28–0.69; p = 0.0004). The incidence of post-ERCP hyperamylasemia also decreased with AH compared to SH (OR = 0.51; p = 0.001). Length of stay decreased by 1 day with AH (Mean Difference (MD): −0.89 d; p = 0.00002). There was no significant difference in adverse events related to fluid overload between two groups (OR:1.29; p = 0.81) and post-ERCP abdominal pain (OR:0.35; p = 0.17). Numbers of patient to be treated with AH to prevent one episode of PEP was 17. Final results of the meta-analysis were not affected by alternative effect measures or statistical models of heterogeneity. Conclusion: Aggressive hydration is associated with a significantly lower incidence of PEP and it appears to be an effective and safe strategy for the prevention of Post ERCP pancreatitis.
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Interrupted Monosyllabic Words: The Effects of Ten Interruption Locations on Recognition Performance by Older Listeners With Sensorineural Hearing LossWilson, Richard H., Sharrett, Kadie C. 01 January 2017 (has links)
Background: Two previous experiments from our laboratory with 70 interrupted monosyllabic words demonstrated that recognition performance was influenced by the temporal location of the interruption pattern. The interruption pattern (10 interruptions/sec, 50% duty cycle) was always the same and referenced word onset; the only difference between the patterns was the temporal location of the onand off-segments of the interruption cycle. In the first study, both young and older listeners obtained better recognition performances when the initial on-segment coincided with word onset than when the initial on-segment was delayed by 50 msec. The second experiment with 24 young listeners detailed recognition performance as the interruption pattern was incremented in 10-msec steps through the 0-To 90-msec onset range. Across the onset conditions, 95% of the functions were either flat or U-shaped. Purpose: To define the effects that interruption pattern locations had on word recognition by older listeners with sensorineural hearing loss as the interruption pattern incremented, re: Word onset, from 0 to 90 msec in 10-msec steps. Research Design: A repeated-measures design with ten interruption patterns (onset conditions) and one uninterruption condition. Study Sample: Twenty-four older males (mean = 69.6 yr) with sensorineural hearing loss participated in two 1-hour sessions. The three-frequency pure-Tone average was 24.0 dB HL and word recognition was $80% correct. Data Collection and Analyses: Seventy consonant-vowel nucleus-consonant words formed the corpus of materials with 25 additional words used for practice. For each participant, the 700 interrupted stimuli (70 words by 10 onset conditions), the 70 words uninterrupted, and two practice lists each were randomized and recorded on compact disc in 33 tracks of 25 words each. Results: The data were analyzed at the participant and word levels and compared to the results obtained earlier on 24 young listeners with normal hearing. The mean recognition performance on the 70 words uninterrupted was 91.0% with an overallmean performance on the ten interruption conditions of 63.2% (range: 57.9-69.3%), compared to 80.4% (range: 73.0-87.7%) obtained earlier on the young adults. The best performances were at the extremes of the onset conditions. Standard deviations ranged from 22.1% to 28.1% (24 participants) and from 9.2% to 12.8% (70 words). An arithmetic algorithm categorized the shapes of the psychometric functions across the ten onset conditions.With the older participants in the current study, 40% of the functions were flat, 41.4% were U-shaped, and 18.6% were inverted U-shaped, which compared favorably to the function shapes by the young listeners in the earlier study of 50.0%, 41.4%, and 8.6%, respectively. There were two words on which the older listeners had 40% better performances. Conclusion: Collectively, the data are orderly, but at the individual word or participant level, the data are somewhat volatile, which may reflect auditory processing differences between the participant groups. The diversity of recognition performances by the older listeners on the ten interruption conditions with each of the 70 words supports the notion that the term hearing loss is inclusive of processes well beyond the filtering produced by end-organ sensitivity deficits.
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"Pedagogen är verktyget"Henriksson, Annica, Schmidt, Veronica January 2019 (has links)
Studiens syfte är att lyfta pedagogernas möjligheter att göra anpassningar på avdelningen och extra stöd till de barn som behöver detta. Vilka professioner har de till sin hjälp och vad tillåter de ekonomiska resurserna? Studien ska förstås genom det sociokulturella perspektivet och den proximala utvecklingszonen. Vi förhåller oss inom olika perspektiv i specialpedagogiken: det kompensatoriska, det kritiska och dilemma perspektivet. Studien belyser också barnet och pedagogen som en social konstruktion som måste förhålla sig till det som anses vara normalt just här och nu.I denna studien har vi valt att titta på hur pedagoger på två olika förskolor anpassar miljön och verksamheten för barn med särskilda behov. Samt om pedagogerna upplever att det är någon skillnad i anpassningsmöjligheterna beroende på om barnet har någon fastställd diagnos eller ej. Slutsatsen i vår studie visar att pedagogerna på förskolorna vi undersökt anser att de har goda förutsättningar för att lyckas genomföra anpassningar. De upplever att de får den utbildning och det stöd de behöver från chefer och specialpedagoger. På den ena förskolan kunde de dock uppleva att det blev skillnader i kompetenserna kring anpassningarna som berodde på att barn med diagnoser har ett större nätverk med tex läkare, psykologer och habiliteringspersonal kring sig än barn utan diagnos. Dessa kompetenser samverkar med förskolans pedagoger vilket kan leda till att det kan bli skillnad i kvalitén på anpassningarna.
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A Study on Distribution Learning of Generative Adversarial NetworksLiu, Jiaping 27 October 2020 (has links)
This thesis is an exploration of the properties of shallow generative adversarial networks (GANs). We focus on several aspects of GANs to investigate the learnability of a class of distributions using shallow GANs and conduct experiments to explore the influence of these aspects on the performance of the GAN models. We identify and analyze several pathological phenomena in theoretical analysis and experiments, and propose potential solutions for them.
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