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Statistical Tests (statistical + test)
Kinds of Statistical Tests Selected AbstractsA STATISTICAL TEST OF UNBIASED EVOLUTION OF BODY SIZE IN BIRDSEVOLUTION, Issue 12 2002Folmer Bokma Abstract., Of the approximately 9500 bird species, the vast majority is small-bodied. That is a general feature of evolutionary lineages, also observed for instance in mammals and plants. The avian interspecific body size distribution is right-skewed even on a logarithmic scale. That has previously been interpreted as evidence that body size evolution has been biased. However, a procedure to test for unbiased evolution from the shape of body size distributions was lacking. In the present paper unbiased body size evolution is defined precisely, and a statistical test is developed based on Monte Carlo simulation of unbiased evolution. Application of the test to birds suggests that it is highly unlikely that avian body size evolution has been unbiased as defined. Several possible explanations for this result are discussed. A plausible explanation is that the general model of unbiased evolution assumes that population size and generation time do not affect the evolutionary variability of body size; that is, that micro- and macroevolution are decoupled, which theory suggests is not likely to be the case. [source] Testing Features of Graphical DIF: Application of a Regression Correction to Three Nonparametric Statistical TestsJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 4 2006Daniel M. Bolt Inspection of differential item functioning (DIF) in translated test items can be informed by graphical comparisons of item response functions (IRFs) across translated forms. Due to the many forms of DIF that can emerge in such analyses, it is important to develop statistical tests that can confirm various characteristics of DIF when present. Traditional nonparametric tests of DIF (Mantel-Haenszel, SIBTEST) are not designed to test for the presence of nonuniform or local DIF, while common probability difference (P-DIF) tests (e.g., SIBTEST) do not optimize power in testing for uniform DIF, and thus may be less useful in the context of graphical DIF analyses. In this article, modifications of three alternative nonparametric statistical tests for DIF, Fisher's ,2test, Cochran's Z test, and Goodman's U test (Marascuilo & Slaughter, 1981), are investigated for these purposes. A simulation study demonstrates the effectiveness of a regression correction procedure in improving the statistical performance of the tests when using an internal test score as the matching criterion. Simulation power and real data analyses demonstrate the unique information provided by these alternative methods compared to SIBTEST and Mantel-Haenszel in confirming various forms of DIF in translated tests. [source] Statistical Tests Based on New Composite Hypotheses in Clinical Trials Reflecting the Relative Clinical Importance of Multiple Endpoints QuantitativelyBIOMETRICAL JOURNAL, Issue 5 2009Masako Nishikawa Abstract In clinical trials, several endpoints (EPs) are often evaluated to compare treatments in some therapeutic area. Suppose that there are two EPs in a clinical trial. We propose a new set of composite hypotheses for continuous variables, taking the relative clinical importance of the EPs into account. The main hypotheses were formulated to show that a treatment is so superior to the control treatment, which is not necessarily a placebo, in one EP, that the possible non-inferiority of the treatment by at most a certain value in the other EP can be compensated sufficiently, taking the clinical point of view into account. The maximum non-inferiority margin of one EP might not be a biologically unimportant difference in exchange for much superiority of the other EP. This formulation leads to a new composite EP and a very simple test statistic. The intersection-union principle was employed to derive the proposed test. [source] Statistical Tests for ClonalityBIOMETRICS, Issue 2 2007Colin B. Begg Summary Cancer investigators frequently conduct studies to examine tumor samples from pairs of apparently independent primary tumors with a view to determine whether they share a "clonal" origin. The genetic fingerprints of the tumors are compared using a panel of markers, often representing loss of heterozygosity (LOH) at distinct genetic loci. In this article we evaluate candidate significance tests for this purpose. The relevant information is derived from the observed correlation of the tumors with respect to the occurrence of LOH at individual loci, a phenomenon that can be evaluated using Fisher's exact test. Information is also available from the extent to which losses at the same locus occur on the same parental allele. Data from these combined sources of information can be evaluated using a simple adaptation of Fisher's exact test. The test statistic is the total number of loci at which concordant mutations occur on the same parental allele, with higher values providing more evidence in favor of a clonal origin for the two tumors. The test is shown to have high power for detecting clonality for plausible models of the alternative (clonal) hypothesis, and for reasonable numbers of informative loci, preferably located on distinct chromosomal arms. The method is illustrated using studies to identify clonality in contralateral breast cancer. Interpretation of the results of these tests requires caution due to simplifying assumptions regarding the possible variability in mutation probabilities between loci, and possible imbalances in the mutation probabilities between parental alleles. Nonetheless, we conclude that the method represents a simple, powerful strategy for distinguishing independent tumors from those of clonal origin. [source] Aerial photosieving of exposed gravel bars for the rapid calibration of airborne grain size mapsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2010Stephen J. Dugdale Abstract In recent years, fluvial remote sensing has seen considerable progress in terms of methods capable of system scale characterisation of river catchments. One key development is automated grain size mapping. It has been shown that high resolution aerial photography can be used to automatically produce grain size maps over entire rivers. However, current aerial grain size mapping procedures all require field calibration data. The collection of such data can be costly and problematic in the case of remote areas. This paper presents a method developed to remove the need for field based calibration data. Called ,aerial photosieving', this method consists of using the same very high resolution aerial imagery intended for grain size map production to visually measure particle sizes on-screen in order to provide calibration data. The paper presents a rigorous comparison of field-based photosieving calibration data and aerial photosieving calibration data. Statistical tests are used to demonstrate that aerial photosieving gives similar results when compared with field-based data with only a slight systematic overprediction. The new aerial photosieving method therefore simplifies the overall procedure required for the production of grain size maps and thus improves the cost-effectiveness and potential availability of this new fluvial remote sensing technology. Copyright © 2010 John Wiley &Sons, Ltd. [source] Evaluation of Cu,Ethylenediamine Metal Ion Buffers as Calibrants for Ion-Selective Electrode Measurement of Copper in Fresh Water SystemsELECTROANALYSIS, Issue 10 2005Ling Zeng Abstract An investigation was made into the accuracy of cupric ion selective electrode (ISE) measurement of Cu in solutions approximating acidic freshwaters with Cu-ethylenediamine buffers used as the calibrants. This method overestimates the free Cu compared with calibration using Cu(NO3)2 standards, the standard addition method, and speciation modelling calculations. Statistical tests showed a small, but significant, difference between the intercepts of the linear Nernstian regressions of the calibration plots of Cu-en buffer standardisation and direct calibration with Cu(NO3)2 standards in matrix that matches the samples. The difference in the intercepts, which corresponds with Eo values of the electrode, is not well understood, but is possibly caused by potentially interfering cations such as Fe2+. The results of this study showed that down to 10,8,M Cu2+, where a linear Nernstian response is possible, the Cu ISE is probably better calibrated using Cu standards prepared in the same matrix as the sample solutions to avoid potential matrix effects. [source] Statistical tests and power analysis for three in-vivo bioassays to determine the quality of marine sedimentsENVIRONMETRICS, Issue 3 2002Nelly van der Hoeven Abstract Statistical tests are recommended for three marine sediment in-vivo bioassays. In two bioassays (Corophium volutator and Echinocardium cordatum), the mortality in the sediment is compared with that in a control. An unconditional 2,×,2 test is recommended. For one bioassay (Rotoxkit MTM with Brachionus plicatilis), mortality in a dilution series of pore water is compared with the mortality in a control. The Williams test for trends is recommended. For each of these tests the power to assess an effect has been calculated. The number of replicates recommended in the standardized test protocol only allows large effects to be observed in almost all (95 per cent) of the experiments. Given the control mortality rates estimated from a large set of controls, a power of 95 per cent will only be reached if the mortality rate in the tested sediment is over 30 per cent for C. volutator and almost 60 per cent for E. cordatum. To reach this power for bioassays with B. plicatilis, where five concentrations are compared with a control, the mortality rate in the lowest effect concentration should be about 35 per cent. As an alternative to no effect testing, it is suggested that whether the effect of a treatment remains below some chosen minimal relevant effect (MRE) should be tested. Given an MRE at a fixed mortality rate of 25 per cent and ,,=,0.05, at least 55 individuals are necessary to be reasonably sure (95 per cent) that a mortality of 10 per cent will not be declared toxic incorrectly. The tests for mortality are based on the assumption that the survival probabilities of individuals within a test vessel are independent. We have described a method to test this assumption and applied it to the data on C. volutator. Copyright © 2002 John Wiley & Sons, Ltd. [source] Genomic context of paralogous recombination hotspots mediating recurrent NF1 region microdeletionGENES, CHROMOSOMES AND CANCER, Issue 1 2004Stephen H. Forbes Recombination between paralogs that flank the NF1 gene at 17q11.2 typically results in a 1.5-Mb microdeletion that includes NF1 and at least 13 other genes. We show that the principal sequences responsible are two 51-kb blocks with 97.5% sequence identity (NF1REP-P1-51 and NF1REP-M-51). These blocks belong to a complex group of paralogs with three components on 17q11.2 and another on 19p13.13. Breakpoint sequencing of deleted chromosomes from multiple patients revealed two paralogous recombination hot spots within the 51-kb blocks. Lack of sequence similarity between these sites failed to suggest or corroborate any putative cis -acting recombinogenic motifs. However, the NF1REPs showed relatively high alignment mismatch between recombining paralogs, and we note that the NF1REP hot spots were regions of good alignment bordered by relatively large alignment gaps. Statistical tests for gene conversion detected a single significant tract of perfect match between the NF1REPs that was 700 bp long and coincided with PRS2, the predominant recombination hot spot. Tracts of perfect match occurring by chance may contribute to breakpoint localization, but our result suggests that perfect tracts at recombination hot spots may be a result of gene conversion at sites at which preferential pairing occurs for other, as-yet-unknown reasons. © 2004 Wiley-Liss, Inc. [source] An Empirical Taxonomy of Hospital Governing Board RolesHEALTH SERVICES RESEARCH, Issue 4 2008Shoou-Yih D. Lee Objective. To develop a taxonomy of governing board roles in U.S. hospitals. Data Sources. 2005 AHA Hospital Governance Survey, 2004 AHA Annual Survey of Hospitals, and Area Resource File. Study Design. A governing board taxonomy was developed using cluster analysis. Results were validated and reviewed by industry experts. Differences in hospital and environmental characteristics across clusters were examined. Data Extraction Methods. One-thousand three-hundred thirty-four hospitals with complete information on the study variables were included in the analysis. Principal Findings. Five distinct clusters of hospital governing boards were identified. Statistical tests showed that the five clusters had high internal reliability and high internal validity. Statistically significant differences in hospital and environmental conditions were found among clusters. Conclusions. The developed taxonomy provides policy makers, health care executives, and researchers a useful way to describe and understand hospital governing board roles. The taxonomy may also facilitate valid and systematic assessment of governance performance. Further, the taxonomy could be used as a framework for governing boards themselves to identify areas for improvement and direction for change. [source] The role of family of origin food-related experiences in bulimic symptomatologyINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 2 2001Elizabeth K. MacBrayer Abstract Objective With the goal of developing a model relating family of origin experiences to maladaptive cognitions to bulimic symptom formation, the authors developed a measure of family of origin food-related experiences called the Family History Inventory. Method A number (N = 662) of sixth to eighth-grade adolescents completed the inventory, eating and dieting expectancy measures, and the Bulimia Test-Revised (BULIT-R). Results Fourteen scales were identified in the inventory. They emphasized family teasing about weight, negative maternal modeling regarding food, and family rules concerning eating. Eleven of the 14 scales correlated with the BULIT-R. Two superordinate factors called Family Teasing and Negative Maternal Modeling summarized 8 of the 14 subscales. Statistical tests were consistent with the hypothesis that eating and dieting expectancies mediate the influence of Family Teasing and Negative Maternal Modeling on bulimic symptomatology. Discussion There was good evidence for the validity of the Family History Inventory. The theoretical implications of the mediation tests are discussed. © 2001 by John Wiley & Sons, Inc. Int J Eat Disord 30: 149,160, 2001 [source] The net barter terms of trade: A smooth transition approachINTERNATIONAL JOURNAL OF FINANCE & ECONOMICS, Issue 1 2003Anna Persson Abstract This paper analyses the net barter terms of trade measured by the primary commodity price index relative to the indexes of unit values of export of manufactures from industrial countries. The starting point is that the series is stationary but possibly non-linear. Statistical tests indicate that the logarithmed series is non-linear and we estimate a Smooth Transition Autoregressive model to describe the process. The dynamics of the model are illustrated by use of parametrically estimated local spectra and generalized impulse response functions. Our model encompasses models from several previous studies, and our conclusion is that the starting point very much decides the outcome. Copyright © 2003 John Wiley & Sons, Ltd. [source] A procedural guide to metacarpal radiogrammetry in archaeologyINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1 2004R. Ives Abstract The technique of metacarpal radiogrammetry was devised in 1960 as a clinical method to aid in the identification of thinned cortical bone, which may help in diagnosis of osteoporosis. Through taking measurements from radiographs, calculations of the amount of cortical bone can be made. The technique is relatively simple and is not destructive. This paper examines the value of the application of this technique to archaeological remains. A standardized methodology of bone assessment is incorporated to enhance the comparability of future research. Statistical tests demonstrate that the technique is robust, as the position of the bone on the film, radiographic enlargement and use of either the left or right metacarpal will not affect the results obtained. However, differences in film type and measurement position can introduce unacceptable variance into the results. Therefore, guidance is given on future applications of the technique. The technique does have value as a widely available, non-destructive technique for assessing cortical bone loss and the probable prevalence of osteoporosis in archaeological collections. Copyright © 2004 John Wiley & Sons, Ltd. [source] Testing Option Pricing Models with Stochastic Volatility, Random Jumps and Stochastic Interest RatesINTERNATIONAL REVIEW OF FINANCE, Issue 3-4 2002George J. Jiang In this paper, we propose a parsimonious GMM estimation and testing procedure for continuous-time option pricing models with stochastic volatility, random jump and stochastic interest rate. Statistical tests are performed on both the underlying asset return model and the risk-neutral option pricing model. Firstly, the underlying asset return models are estimated using GMM with valid statistical tests for model specification. Secondly, the preference related parameters in the risk-neutral distribution are estimated from observed option prices. Our findings confirm that the implied risk premiums for stochastic volatility, random jump and interest rate are overall positive and varying over time. However, the estimated risk-neutral processes are not unique, suggesting a segmented option market. In particular, the deep ITM call (or deep OTM put) options are clearly priced with higher risk premiums than the deep OTM call (or deep ITM put) options. Finally, while stochastic volatility tends to better price long-term options, random jump tends to price the short-term options better, and option pricing based on multiple risk-neutral distributions significantly outperforms that based on a single risk-neutral distribution. [source] The ratification of ILO Conventions and the provision of unemployment benefits: An empirical analysisINTERNATIONAL SOCIAL SECURITY REVIEW, Issue 1 2010Wonik Kim Abstract This article tests the relationship between the ratification of International Labour Organization (ILO) Conventions and the provision of unemployment benefits. Statistical tests focus on two related issues: why countries ratify ILO Conventions on unemployment benefits, and whether ratification influences government spending on unemployment benefits. The main findings are that democracy, region, income, and globalization are the main factors influencing why countries ratify ILO Conventions on unemployment benefits. In turn, the ratification of ILO Conventions is systematically associated with higher spending if countries have ratified more than two Conventions. [source] Constrained price, address, or logit brand demand models: An econometric comparison in the Boston fluid milk marketAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 2 2005Li Tian This article estimates a general linear demand model for three fluid milk brands. It finds perverse signs and complementarity among these substitutes. We develop three constrained models to eliminate perverse signs: a price conduct constraint in the linear model that links private label and Garelick pricing, a generalized Mills address model, and the logit model. Statistical tests indicate that each of the three constrained models produces acceptable substitution patterns and that none is preferred to the other two. On nonstatistical grounds, however, the Mills and price-constrained models perform best. This is the first empirical study of the Mills address model of private-label pricing. Finally, we demonstrate that estimated price-reaction functions and the corresponding total elasticities, which capture only strategic non-collusive interaction in these Nash Bertrand models, provide interesting insight into competition among brands. EconLit citation: L670, L130.] © 2005 Wiley Periodicals, Inc. Agribusiness 21: 149,166, 2005. [source] Robustness of alternative non-linearity tests for SETAR modelsJOURNAL OF FORECASTING, Issue 3 2004Wai-Sum Chan Abstract In recent years there has been a growing interest in exploiting potential forecast gains from the non-linear structure of self-exciting threshold autoregressive (SETAR) models. Statistical tests have been proposed in the literature to help analysts check for the presence of SETAR-type non-linearities in an observed time series. It is important to study the power and robustness properties of these tests since erroneous test results might lead to misspecified prediction problems. In this paper we investigate the robustness properties of several commonly used non-linearity tests. Both the robustness with respect to outlying observations and the robustness with respect to model specification are considered. The power comparison of these testing procedures is carried out using Monte Carlo simulation. The results indicate that all of the existing tests are not robust to outliers and model misspecification. Finally, an empirical application applies the statistical tests to stock market returns of the four little dragons (Hong Kong, South Korea, Singapore and Taiwan) in East Asia. The non-linearity tests fail to provide consistent conclusions most of the time. The results in this article stress the need for a more robust test for SETAR-type non-linearity in time series analysis and forecasting. Copyright © 2004 John Wiley & Sons, Ltd. [source] Nutrient intake of children consuming breakfast at school clubs in LondonJOURNAL OF HUMAN NUTRITION & DIETETICS, Issue 5 2003S. Waddington Introduction: Research into the effectiveness of breakfast clubs has most commonly focused on social benefits to the child and school, such as improved attendance at school, punctuality and improved concentration levels in the classroom (UEA, 2002). Limited research has been undertaken to investigate the nutritional value of the breakfast foods on offer, or the nutritional content of foods consumed by the child. The aim of this study was to find out what children eat and drink at school breakfast clubs in London. Method: The sample population consisted of 98 children (39 boys and 59 girls) aged 5,11 years attending four primary schools in London. Data were collected about the food on offer and the pricing of different food items, demographic data about the children attending the school club, qualitative data on food preferences and a weighed food intake on two different occasions for each child. Statistical tests (anova and chi-squared tests) and nutrient analysis using Comp-Eat were carried out. Results: The average nutrient content of the breakfast meal consumed was 330 kcal, 12 g protein, 11 g fat and 49 g carbohydrate. Variation was seen between schools. Generally intakes of vitamin C, calcium and sodium were high and intakes of iron were average. anova between schools showed statistically significant results for a number of nutrients , protein, fat, saturated fat, carbohydrate, sugar, calcium and sodium. Boys were consuming statistically significantly more fat, saturated fat and calcium than girls. One in five children did not have a drink at breakfast. Menu options and pricing of food items varied between the schools and it was noted to influence children's food choice and consumption. Mean energy intakes equated to 18% of the estimated average requirement for boys and 20% for girls, with girls consuming more carbohydrate and sugar, and boys consumed more fat and protein. Discussion: The findings suggest that careful planning of menus should be undertaken with cereal-based options being offered daily and cooked options only occasionally, and that healthier eating messages can be incorporated effectively into school clubs when supported by the whole school approach to healthy eating. Conclusion: Food offered at school breakfast clubs can contribute substantial nutrients to a child's daily intake and therefore a varied menu, and guided food choices, should be developed incorporating healthier nutrient rich options. This work was supported by Brooke Bond working in partnership with the BDA Community Nutrition Group. [source] Simultaneous intravenous and intramiddle-ear dosing to determine cefditoren influx and efflux clearances in middle ear fluid in freely moving chinchillasJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2003Tong Zhu Abstract This study was conducted to determine cefditoren (CDTR) transport kinetics between plasma and middle ear fluid (MEF) by characterizing influx (CLin) and efflux (CLout) clearances expressed in terms of unbound concentrations and their ratio. Simultaneous intravenous bolus and intramiddle-ear dose were administered to two groups of chinchillas: normal control and infected. In vivo microdialysis was employed to determine protein-unbound CDTR levels in MEF. Compartmental and noncompartmental analysis was performed. Parameters determined in both groups were compared to assess the effect of infection and inflammation on CDTR distribution kinetics. CLin and CLout estimates obtained by compartmental and noncompartmental analysis agreed well. The calculated CLin/CLout ratio was 0.76,±,0.23 and 0.56,±,0.25 in normal (n,=,9) and infected (n,=,6) animals, respectively. The 95% confidence interval of this ratio in both groups does not include unity. Statistical tests showed no difference (p,>,0.05) in CLin, CLout, and their ratio between the two groups. In conclusion, middle ear infection and inflammation does not affect CDTR distribution. The CLin/CLout ratio determined in chinchillas compares well with values estimated from data in pediatric patients. An active efflux mechanism in middle ear mucosa may be involved in CDTR distribution in MEF. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1947,1956, 2003 [source] Splitting the Baby: An Empirical Test of Rules of Thumb in Regulatory Price SettingKYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 3 2005T. Randolph Beard Summary This article provides an empirical evaluation of a recent and important exercise in regulatory price setting in the United States. The 1996 Telecommunications Act required incumbent local phone companies to sell components of their network to rival firms at regulated prices, and the prices for these ,unbundled network elements' were based primarily on independent estimates of forward-looking economic costs. Our econometric analysis reveals that, while cost is a primary determinant of element prices, the prices also reflect foregone retail profits for incumbent firms. Statistical tests suggest that ,splitting the baby' is an accurate positivist description of public agency behavior. [source] Statistical evaluation of diffusion-weighted imaging of the human kidneyMAGNETIC RESONANCE IN MEDICINE, Issue 2 2010Hans-Jörg Wittsack Abstract The signal of diffusion-weighted imaging of the human kidney differs from the signal in brain examinations due to the different microscopic structure of the tissue. In the kidney, the deviation of the signal behavior of monoexponential characteristics is pronounced. The aim of the study was to analyze whether a mono- or biexponential or a distribution function model fits best to describe diffusion characteristics in the kidney. To determine the best regression, different statistical parameters were utilized: correlation coefficient (R2), Akaike's information criterion, Schwarz criterion, and F-test (Fratio). Additionally, simulations were performed to analyze the relation between the different models and their dependency on signal noise. Statistical tests showed that the biexponential model describes the signal of diffusion-weighted imaging in the kidney better than the distribution function model. The monoexponential model fits the diffusion-weighted imaging data the least but is the most robust against signal noise. From a statistical point of view, diffusion-weighted imaging of the kidney should be modeled biexponentially under the precondition of sufficient signal to noise. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] Rotational velocities of the giants in symbiotic stars , III.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008Evidence of fast rotation in S-type symbiotics ABSTRACT We have measured the projected rotational velocities (v sin i) in a number of symbiotic stars and M giants using high-resolution spectroscopic observations. On the basis of our measurements and data from the literature, we compare the rotation of mass donors in symbiotics with v sin i of field giants and find that: (i) the K giants in S-type symbiotics rotate at v sin i > 4.5 km s,1, which is 2,4 times faster than the field K giants; (ii) the M giants in S-type symbiotics rotate on average 1.5 times faster than the field M giants. Statistical tests show that these differences are highly significant , p-value <10,3 in the spectral-type bins K2III-K5III, M0III-M6III and M2III-M5III and (iii) our new observations of D'-type symbiotics also confirm that they are fast rotators. As a result of the rapid rotation, the cool giants in symbiotics should have 3,30 times larger mass-loss rates. Our results suggest also that bipolar ejections in symbiotics seem to happen in objects where the mass donors rotate faster than the orbital period. All spectra used in our series of papers can be obtained upon request from the authors. [source] A trend filtering algorithm for wide-field variability surveysMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005Géza Kovács ABSTRACT We show that various systematics related to certain instrumental effects and data reduction anomalies in wide-field variability surveys can be efficiently corrected by a trend filtering algorithm (TFA) applied to the photometric time-series produced by standard data pipelines. Statistical tests, performed on the data base of the HAT Network project, show that by the application of this filtering method the cumulative detection probability of periodic transits increases by up to 0.4 for variables brighter than 11 mag, with a trend of increasing efficiency toward brighter magnitudes. We also show that the TFA can be used for the reconstruction of periodic signals by iteratively filtering out systematic distortions. [source] Effect of an intravenous single dose of ketamine on postoperative pain in tonsillectomy patientsPEDIATRIC ANESTHESIA, Issue 9 2006MARIO JOSE DA CONCEIÇÃO MSC MD TSA Summary Background:, Tonsillectomy has a high incidence of postoperative pain. The aim of the present study was to determine whether the use of low-dose IV ketamine, before the start of surgery or after the end of the operation, would lead to significantly improved pain control after tonsillectomy in pediatric patients. Methods:, Ninety children, 5,7 years old, scheduled for elective tonsillectomy were randomly assigned to one of three groups of 30 patients each; groups I, II and III. Patients in group I received no ketamine. Patients in group II received 0.5 mg·kg,1 of ketamine before the surgical start and for group III the same dose was given after the operation ended. Postoperative pain was scored by the Oucher scale. Systolic and diastolic pressures and heart rate were recorded perioperatively. Unwanted side effects were recorded by the ward staff personnel on a 24-h study-specific questionnaire. Statistical tests consisted of Student's t -test, chi-square and anova as appropriated. Results:, The number of patients complaining of pain was greater in group I compared with patients in groups II and III with a significative statistical difference (P < 0.05). The degree of postoperative pain was significantly higher in patients of group I compared with groups II and III (P < 0.05). Eight patients in group I needed rescue doses of morphine, three for group II and none for group III. In group I, three of eight patients required two doses of morphine during the first 249h postoperatively. No unwanted side effects were noted. Conclusions:, The use of a single small dose of ketamine in a pediatric population undergoing tonsillectomy could reduce the frequency or even avoid the use of rescue analgesia in the postoperative period independent of whether used before or after the surgical procedure. [source] Manipulating Electoral Rules to Manufacture Single-Party DominanceAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 1 2008Kenneth Mori McElwain This article argues that the LDP manufactured its parliamentary dominance in postwar Japan by strategically altering specific facets of the electoral system. More generally, I demonstrate that intraparty politics play a crucial role in determining when and how electoral rules are changed. Despite widespread evidence that the LDP would win more seats under an SMP electoral formula, party leaders were repeatedly blocked from replacing the postwar MMD-SNTV system by intraparty incumbents, who feared that such a change would harm their individual reelection prospects. However, party leaders had greater leeway in altering rules that generated fewer intraparty conflicts. Between 1960 and 1990, the LDP implemented approximately fifty changes to campaign regulations, most of which were aimed at enhancing the incumbency advantage of all rank-and-file MPs. Statistical tests confirm that absent pro-incumbent revisions to the electoral code, the LDP would have succumbed to declining public popularity and lost its majority at least a decade earlier. [source] Strategy Similarity and Coordination,THE ECONOMIC JOURNAL, Issue 497 2004Rajiv Sarin In the payoff assessment model of choice (Sarin and Vahid, 1999), only the assessment of the chosen strategy is updated. We extend that model to allow the agent to also update the assessments of strategies that the agent thinks are similar to the chosen strategy. We use this model to explain observed behaviour in a recent experiment. Statistical tests cannot distinguish between the payoff distributions generated by the model and the observed payoff distributions in almost every period. [source] Self-assessment of voice therapy for chronic dysphoniaCLINICAL OTOLARYNGOLOGY, Issue 1 2004R. Speyer Self-assessment of voice therapy for chronic dysphonia The effects of voice therapy in a group of chronically dysphonic patients are determined using two quality-of-life (QOL) instruments: the Voice Handicap Index (VHI), and a simple three-item outcome scale (three visual analogue scales). Both instruments measure changes in the quality of the voice itself and in the extent of impairment resulting from the dysphonia as experienced by the patient in social and occupational settings. Statistical tests conducted on pre- and post-treatment data indicated significant improvements on both instruments for the group as a whole. At the individual level, however, the effects were diverse. For roughly 50% of the subjects, a significant improvement could be established. The positive changes as measured with the three-item scale were greater than those measured with the VHI. The results suggest that the two QOL instruments measure slightly different aspects of the subjective perception of the therapy effects. In order to obtain a general evaluation of the patient's handicap, it may suffice to ask some simple questions. [source] Microchimerism and rejection: a meta-analysisCLINICAL TRANSPLANTATION, Issue 4 2000Amrik Sahota Aims. To study the relationship between graft rejection and microchimerism with and without donor bone marrow infusion in recipients of kidney, liver, heart and lung transplants. Selection of manuscripts. Thirty-seven manuscripts presenting clinical data on microchimerism and rejection, published between 1991 and 1997, were identified. Of these, 16 were excluded due to duplication or insufficient data. Inclusion criteria were data on microchimerism, bone marrow infusion and rejection episodes. Statistical tests. A mixed effect logistic model was used to test for homogeneity of transplant centers. The centers were found to be homogeneous for rejection rates controlling for microchimerism and bone marrow infusion. Using rejection episodes at 3, 6, and 12 months post-transplant as the outcome, we evaluated logistic regression models to derive odds ratios for rejection with microchimerism and with bone marrow infusion for each organ. Results. Microchimerism was generally associated with a higher incidence of acute rejection for heart, lung, and kidney transplants and a lower incidence for liver transplants, especially at 12 months and above. Bone marrow infusion decreased the risk of acute rejection for heart transplants and increased the risk for lung and, to a lesser extent, for liver transplants. No consistent effect was seen in kidney transplants. At 12 months and longer, microchimerism was associated with a decreased incidence of chronic rejection in recipients of lung transplants, but there were insufficient data to determine this outcome for other organs. Conclusions. (i) Microchimerism was detected in the majority of patients. (ii) The effect of microchimerism and bone marrow infusion on rejection episodes varied with the organ and, for a given organ, it was time-dependent. (iii) These findings demonstrate the need for more extensive studies on microchimerism and donor-specific hyporesponsiveness. [source] Active Learning through Modeling: Introduction to Software Development in the Business Curriculum,DECISION SCIENCES JOURNAL OF INNOVATIVE EDUCATION, Issue 2 2004Boris Roussev ABSTRACT Modern software practices call for the active involvement of business people in the software process. Therefore, programming has become an indispensable part of the information systems component of the core curriculum at business schools. In this paper, we present a model-based approach to teaching introduction to programming to general business students. The theoretical underpinnings of the new approach are metaphor, abstraction, modeling, Bloom's classification of cognitive skills, and active learning. We employ models to introduce the basic programming constructs and their semantics. To this end, we use statecharts to model object's state and the environment model of evaluation as a virtual machine interpreting the programs written in JavaScript. The adoption of this approach helps learners build a sound mental model of the notion of computation process. Scholastic performance, student evaluations, our experiential observations, and a multiple regression statistical test prove that the proposed ideas improve the course significantly. [source] An evidence-based appraisal of splinting luxated, avulsed and root-fractured teethDENTAL TRAUMATOLOGY, Issue 1 2008Bill Kahler For this systematic review of splinting of teeth that have been luxated, avulsed or root-fractured, the clinical PICO question is (P) what are splinting intervention decisions for luxated, avulsed and root-fractured teeth (I) considering that the splinting intervention choice may include (i) no splinting, (ii) rigid or functional splinting for the different types of trauma and (iii) different durations of the splinting period (C) when comparing these splinting choices for the different types of trauma and their effect on (O) healing outcomes for the teeth. A keyword search of PubMed was used. Reference lists from identified articles and dental traumatology texts were also appraised. The inclusion criterion for this review was either a multivariate analysis or controlled stratified analyses as many variables have the potential to confound the assessment and evaluation of healing outcomes for teeth that have been luxated, avulsed or root-fractured. A positive statistical test is not proof of a causal conclusion, as a positive statistical relationship can arise by chance, and so this review also appraises animal studies that reportedly explain biological mechanisms that relate to healing outcomes of splinted teeth. The clinical studies were ranked using the ,Centre of Evidence-based Medicine' categorization (levels 1,5). All 12 clinical studies selected were ranked as level 4. The studies generally indicate that the prognosis is determined by the type of injury rather than factors associated with splinting. The results indicate that the types of splint and the fixation period are generally not significant variables when related to healing outcomes. This appraisal identified difficulties in the design of animal experimentation to correctly simulate some dental injuries. Some of the studies employed rigid splinting techniques, which are not representative of current recommendations. Recommended splinting treatment protocols for teeth that have been luxated, avulsed or root-fractured teeth are formulated on the strength of research evidence. Despite the ranking of these studies in this appraisal as low levels of evidence, these recommendations should be considered ,best practice', a core philosophy of evidence-based dentistry. [source] Lower-extremity selective voluntary motor control in patients with spastic cerebral palsy: increased distal motor impairmentDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 3 2010EILEEN G FOWLER Aim, Multiple impairments contribute to motor deficits in spastic cerebral palsy (CP). Selective voluntary motor control (SVMC), namely isolation of joint movement upon request, is important, but frequently overlooked. This study evaluated the proximal to distal distribution of SVMC impairment among lower extremity joints. Method, Using a recently developed tool, the Selective Control Assessment of the Lower Extremity (SCALE), we evaluated the SVMC of the hip, knee, ankle, subtalar joint, and toes in a cross-sectional, observational study of 47 participants with spastic, diplegic, hemiplegic, and quadriplegic CP (22 males, 25 females; mean age 11y 9mo, SD 4y 8mo; Gross Motor Function Classification System levels I,IV). Results, Statistically significant decreases in SCALE scores from hip to toes were found using the Page statistical test for trend (p<0.001). Statistically significant differences (p<0.05) were found between all joint pairs, except toes versus subtalar, toes versus ankle, and right ankle versus subtalar joints. Cross-tabulation of score frequencies for all pairs revealed that proximal joint scores were higher or equal to distal ones 81 to 100% of the time. Excluding toes versus subtalar joints, proximal scores exceeded distal ones 94 to 100% of the time. Interpretation, We confirmed increasing proximal to distal SVMC impairment, which may have implications for treatment and research. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||