Two-sample Kolmogorov-Smirnov Test Research Articles

Heart Rate Variability Dynamics for the Prognosis of Cardiovascular Risk

Statistical, spectral, multi-resolution and non-linear methods were applied to heart rate variability (HRV) series linked with classification schemes for the prognosis of cardiovascular risk. A total of 90 HRV records were analyzed: 45 from healthy subjects and 45 from cardiovascular risk patients. A total of 52 features from all the analysis methods were evaluated using standard two-sample Kolmogorov-Smirnov test (KS-test). The results of the statistical procedure provided input to multi-layer perceptron (MLP) neural networks, radial basis function (RBF) neural networks and support vector machines (SVM) for data classification. These schemes showed high performances with both training and test sets and many combinations of features (with a maximum accuracy of 96.67%). Additionally, there was a strong consideration for breathing frequency as a relevant feature in the HRV analysis.

Evaluation of a dynamic downscaling of precipitation over the Norwegian mainland

In order to assess the potential of regional climate models to be used to project future weather events, a first step is to study the regional model forced by actual weather, or more precisely by reanalysis of weather data. In this paper we investigate how well the Norwegian regional model HIRHAM, forced by ERA-40 reanalysis data, compares to observed precipitation data from the Norwegian Meteorological Institute over Norwegian mainland. This paper aims to show how standard methods of statistical testing may be used to assess dynamic downscaling. Methods considered are the Kolmogorov—Smirnov two-sample test, a Fisher exact test for equality of quantiles, an Extreme Value Theory test, where equality of the 1-yr return levels are tested, and equality of wet-day frequency. All tests are performed seasonally. The regional model is skillful in describing the lower quartile of the precipitation distribution, but underestimates higher levels of precipitation. Our results indicate that the regional model has too many but too small rain events for all seasons

Influences of the biophysical environment on blister rust and mountain pine beetle, and their interactions, in whitebark pine forests

Aim To understand how the biophysical environment influences patterns of infection by non-native blister rust (caused by Cronartium ribicola) and mortality caused by native mountain pine beetles (Dendroctonus ponderosae) in whitebark pine (Pinus albicaulis) communities, to determine how these disturbances interact, and to gain insight into how climate change may influence these patterns in the future. Location High-elevation forests in south-west Montana, central Idaho, eastern and western Oregon, USA. Methods Stand inventory and dendroecological methods were used to assess stand structure and composition and to reconstruct forest history at sixty 0.1-ha plots. Patterns of blister rust infection and mountain pine beetle-caused mortality in whitebark pine trees were examined using nonparametric Kruskal–Wallis ANOVA, Mann–Whitney U-tests, and Kolmogorov–Smirnov two-sample tests. Stepwise regression was used to build models of blister rust infection and mountain pine beetle-related mortality rates based on a suite of biophysical site variables. Results Occurrence of blister rust infections was significantly different among the mountain ranges, with a general gradient of decreasing blister rust occurrence from east to west. Evidence of mountain pine beetle-caused mortality was identified on 83% of all dead whitebark pine trees and was relatively homogenous across the study area. Blister rust infected trees of all ages and sizes uniformly, while mountain pine beetles infested older, larger trees at all sites. Stepwise regressions explained 64% and 58% of the variance in blister rust infection and beetle-caused mortality, respectively, indicating that these processes are strongly influenced by the biophysical environment. More open stand structures produced by beetle outbreaks may increase the exposure of surviving whitebark pine trees to blister rust infection. Main conclusions Variability in the patterns of blister rust infection and mountain pine beetle-caused mortality elucidated the fundamental dynamics of these disturbance agents and suggests that the effects of climate change will be complex in whitebark pine communities and vary across the species’ range. Interactions between blister rust and beetle outbreaks may accelerate declines or facilitate the rise of rust resistance in whitebark pine depending on forest conditions at the time of the outbreak.

A SEARCH FOR RR LYRAE VARIABLES IN THE CENTRAL REGION OF M54

We have analyzed archival Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) observations of the central region of the globular cluster M54. The 12 irregularly timed observations (6 F555W, 6 F814W) were reduced using the HSTphot stellar photometry package. Our statistical analysis of the HSTphot photometry yielded 50 variable stars that are likely RR Lyrae candidates. These candidates were missed by previous ground-based searches for RR Lyraes due to the extreme crowding in the core of M54. We performed two checks on our sample of RR Lyrae candidates to determine how different they were from the other variable candidates. The first test was a numerical analysis comparing the ratio of variable candidates to the total number of stars within the blue horizontal branch, the RR Lyrae region, and the red giant branch. We found ratios of 0.61%, 13%, and 1.1% in these regions, respectively. Our next test was a two-sample Kolmogorov-Smirnov (K-S) test, which allowed us to find out how different our 50 RR Lyrae candidates were from the 50 brightest other variable candidates. According to the K-S test, there is only a 0.0004% probability that these two populations are similar, indicating that our RR Lyrae candidates do indeed exhibit some real fluctuation in their brightness. We sampled the light curves of confirmed RR Lyrae light curves to simulate the HST observing conditions and found that a signature of variability in 2911 out of the 4000 (72%) generated stars. We estimate that there maybe as many as 19 more RR Lyrae candidates that were undetected in the WFPC2 field of view. The presence of additional RR Lyraes has implications into the current Oosterhoff classification for the cluster.

Changes in Precipitation Extremes in the Hawaiian Islands in a Warming Climate

Abstract For the first time, trends of five climate change indices related to extreme precipitation events in the Hawaiian Islands are investigated using daily observational records from the 1950s to 2007. Four indices [simple daily intensity index (SDII), total number of day with precipitation ≥25.4 mm (R25), annual maximum consecutive 5-day precipitation amount (R5d), and the fraction of annual total precipitation from events exceeding the 1961–90 95th percentile (R95p)] describe the intensity (SDII), frequency (R25), and magnitude (R5d and R95p) of precipitation extremes, and the fifth index [consecutive dry days (CDD)] describes drought conditions. The annual probability density functions (PDFs) of precipitation indices for two epochs (i.e., 1950–79 and 1980–2007) are analyzed. Since the 1980s, there has been a change in the types of precipitation intensity, resulting in more frequent light precipitation and less frequent moderate and heavy precipitation intensity. The other three precipitation-related indices (R25, R5d, and R95p) demonstrate a shift toward the left of the distribution over time, suggesting shorter annual number of days with intense precipitation and smaller consecutive 5-day precipitation amounts and smaller fraction of annual precipitation due to events exceeding the 1961–90 95th percentile in the recent epoch relative to the first epoch. The changes of PDF distribution for SDII, R25, R5d, and CDD are significant at the 5% level according to a two-sample Kolmogorov–Smirnov test. A nonparametric trend analysis is then performed for four periods, with different starting years (e.g., the 1950s, the 1960s) but the same ending year (2007). Long-term downward trends are evident for four precipitation-related indices, and long-term upward trends are observed for CDD. Geographically, Kauai and Oahu are dominated by long-term decreasing trends for four precipitation-related indices, while increasing trends play the major role over the island of Hawaii. The upward trends of drought conditions in the long run are predominant on all the major Hawaiian Islands. To investigate whether the trends are stable throughout the time, the derivatives of trends for each of the 30-yr running series are calculated (e.g., 1950–79, 1951–80, … , 1978–2007) for four precipitation-related indices at each station. For Kauai and Oahu, positive derivatives prevail for all indices in the presence of long-term negative trends, suggestive of a phase change in precipitation extremes and such extremes showing an upswing recently. For the island of Hawaii, there is also an indication of phase reversal over the last 60 yr, with negative derivatives occurring in the presence of the background positive trends. A positive relationship is found between the precipitation indices and the Southern Oscillation index (SOI), implying more precipitation extremes during La Niña years and vice versa for El Niño years. Spatial patterns of standardized anomalies of indices are presented for the La Niña/−PDO minus El Niño/+PDO composites.

Detrital zircon provenance from three turbidite depocenters of the Middle-Upper Triassic Songpan-Ganzi complex, central China: Record of collisional tectonics, erosional exhumation, and sediment production

To test the idea that the voluminous upper Middle to Upper Triassic turbidite strata in the Songpan-Ganzi complex of central China archive a detrital record of Dabie ultrahigh-pressure (UHP) terrane unroofing, we report 2080 single detrital U-Pb zircon ages by sensitive high-resolution ion microprobe–reverse geometry (SHRIMP-RG) and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analysis from 29 eastern Songpan-Ganzi complex sandstone samples. Low (<0.07) Th/U zircons, consistent with crystallization under UHP conditions, are rare in eastern Songpan-Ganzi complex zircon, and U-Pb ages of low Th/U zircons are incompatible with a Dabie terrane source. An unweighted pair group method with arithmetic mean nearest-neighbor analysis of Kolmogorov-Smirnov two-sample test results reveals that the eastern Songpan-Ganzi complex is not a single contiguous turbidite system but is instead composed of three subsidiary depocenters, each associated with distinct sediment sources. The northeastern depocenter contains zircon ages characterized by Paleozoic and bimodally distributed Precambrian zircon populations, which, together with south- to southeast-directed paleocurrent data, indicate derivation from the retro-side of the Qinling-Dabie (Q-D) collisional orogen wedge. In the central depocenter, the dominantly Paleozoic detrital zircon signature and south- to southwest-oriented paleocurrent indicators reflect a profusion of Paleozoic zircon grains. These data are inter preted to reflect an influx of material derived from erosion of Paleozoic supra-UHP rocks of the Dabie terrane in the eastern Qinling-Dabie orogen, which we speculate may have been enhanced by development of a monsoonal climate. This suggests that erosional unroofing played a significant role in the initial phase of UHP exhumation and likely influenced the petrotectonic and structural evolution of the Qinling-Dabie orogen, as evidenced by compressed Triassic isotherms/grads reported in the Huwan shear zone that bounds the Dabie terrane to the north. The central depocenter deposits reflect a later influx of bimodally distributed Precambrian zircon, signifying either a decrease in the influx of Paleozoic zircon grains due to stalled UHP exhumation and/or dilution of the same influx of Paleozoic zircons by spilling of Precambrian zircon from the northeastern depocenter into the central depocenter basin, perhaps due to infilling and bypass of sediment from the northern depocenter or due to initial collapse and constriction of the eastern Songpan-Ganzi complex basin. The southeastern depocenter of the eastern Songpan-Ganzi complex bears significant Paleozoic, Neoproterozoic, and Paleoproterozoic zircon populations derived from the South China block and Yidun arc complex, likely recording nascent uplift of the Longmenshan deformation belt due to impingement of the Yidun arc complex upon the western margin of the South China block.

Statistical properties of deep ocean noise.

The various arrays sea test (VAST) was conducted in July 1989 in the northeast Pacific Ocean. A 3000-m-long, 200-element hydrophone array was suspended for an 11-day period from R/P FLIP, moored about halfway between San Diego and Hawaii (34N, 140W). Simultaneously, 12 neutrally buoyant, freely drifting Swallow floats equipped with both infrasonic hydrophones and three-component geophones were deployed at various depths 150 km off the California coast (35N, 122W). The statistical properties of deep ocean noise recorded by these sensor systems, both single element and beam level, are examined quantitatively under a variety of conditions, including wind-dominated (15–18 kt), distant air gun operations, and marine mammal vocalizations. Non-parametric statistical tests applied to narrow band complex time series of the data include the Wald–Wolfowitz run test for mutual independence of the data samples, the Kolmogorov–Smirnov two-sample test for stationarity, and the Kolmogorov–Smirnov one-sample test for Gaussianity. Results are presented over a broad range in frequencies and time scales and show that the noise field at times and in certain directions displays non-stationary and non-Gaussian properties. In a few cases, these statistical characteristics can be associated with specific physical processes. [Work supported by the Office of Naval Research.]

Symptomatic comparison in efficacy on patients with benign prostatic hyperplasia treated with two therapeutic approaches

ObjectivesA randomised controlled trial was performed to compare the symptomatic effects on patients with benign prostatic hyperplasia (BPH) treated by two therapeutic approaches – the Western medicine (WM) and traditional Chinese medicine (TCM).MethodsFour primary outcome measures, namely the quality of life (QOL), maximum urine flow ratio (UFR), International Prostate Symptom Score (IPSS) and prostate volumes, as well as four urethra-related and 35 non-urethra-related symptoms, were investigated to evaluate the effects on 31 BPH patients subjected to WM (Terazosin Hydrochloride Hytrin, THH) and 30 cases to TCM (herbal Saxifrage tablet, HST). The effects of both treatments are compared by the two-sample Kolmogorov–Smirnov test. The contributions of symptoms for four assessments are analysed by the logistic regression model and the Chow test.ResultsThe effect of TCM is weaker than that of WM in the assessment of the IPSS score (p < 0.05), and both treatments are similar in the prostate volumes, the maximum UFR and the QOL assessments (p > 0.05), as well as in the effective number of urethra-related or non-urethra-related symptoms before and after treatment (p > 0.05). By comparing the linear regression models, different urethra-related and non-urethra-related symptom patterns associated with TCM and WM therapies are detected for four assessments, especially for the prostate volume assessment (p < 0.01).ConclusionTCM (HST) is a potentially effective treatment in improving the QOL, prostate volumes and maximum UFR for patients with BPH, though it is less effective in ameliorating the IPSS score when compared with WM (THH). The non-urethra-related symptoms experienced by BPH patients might be one of the parameters to further achieve the tailored diagnosis and treatment for BPH.

STATISTICAL TESTS FOR SCALING IN THE INTER-EVENT TIMES OF EARTHQUAKES IN CALIFORNIA

We explore in depth the validity of a recently proposed scaling law for earthquake inter-event time distributions in the case of the Southern California, using the waveform cross-correlation catalog of Shearer et al. Two statistical tests are used: on the one hand, the standard two-sample Kolmogorov-Smirnov test is in agreement with the scaling of the distributions. On the other hand, the one-sample Kolmogorov-Smirnov statistic complemented with Monte Carlo simulation of the inter-event times, as done by Clauset et al., supports the validity of the gamma distribution as a simple model of the scaling function appearing on the scaling law, for rescaled inter-event times above 0.01, except for the largest data set (magnitude greater than 2). A discussion of these results is provided.

Nonparametric Testing of Distributions—the Epps–Singleton Two-Sample Test using the Empirical Characteristic Function

In statistics, two-sample tests are used to determine whether two samples have been drawn from the same population. An example of such a test is the widely used Kolmogorov–Smirnov two-sample test. There are other distribution-free tests that might be applied in similar occasions. In this article, we describe a two-sample omnibus test introduced by Epps and Singleton, which usually has a greater power than the Kolmogorov–Smirnov test although it is distribution free. The superiority of the Epps–Singleton characteristic function test is illustrated in two examples. We compare the two tests and supplement this contribution with a Stata implementation of the omnibus test.

Single Neuron Ubiquitin-Proteasome Dynamics Accompanying Inclusion Body Formation in Huntington Disease

The accumulation of mutant protein in intracellular aggregates is a common feature of neurodegenerative disease. In Huntington disease, mutant huntingtin leads to inclusion body (IB) formation and neuronal toxicity. Impairment of the ubiquitin-proteasome system (UPS) has been implicated in IB formation and Huntington disease pathogenesis. However, IBs form asynchronously in only a subset of cells with mutant huntingtin, and the relationship between IB formation and UPS function has been difficult to elucidate. Here, we applied single-cell longitudinal acquisition and analysis to monitor mutant huntingtin IB formation, UPS function, and neuronal toxicity. We found that proteasome inhibition is toxic to striatal neurons in a dose-dependent fashion. Before IB formation, the UPS is more impaired in neurons that go on to form IBs than in those that do not. After forming IBs, impairment is lower in neurons with IBs than in those without. These findings suggest IBs are a protective cellular response to mutant protein mediated in part by improving intracellular protein degradation.

Kolmogorov-Smirnov two-sample test based on regression rank scores

We derive the two-sample Kolmogorov-Smirnov type test when a nuisance linear regression is present. The test is based on regression rank scores and provides a natural extension of the classical Kolmogorov-Smirnov test. Its asymptotic distributions under the hypothesis and the local alternatives coincide with those of the classical test.

Cellular Mechanisms Underlying Stimulus-Dependent Gain Modulation in Primary Visual Cortex Neurons In Vivo

Gain modulation is a widespread neuronal phenomenon that modifies response amplitude without changing selectivity. Computational and in vitro studies have proposed cellular mechanisms of gain modulation based on the postsynaptic effects of background synaptic activation, but these mechanisms have not been studied in vivo. Here, we used intracellular recordings from cat primary visual cortex to measure neuronal gain while changing background synaptic activity with visual stimulation. We found that increases in the membrane fluctuations associated with increases in synaptic input do not obligatorily result in gain modulation in vivo. However, visual stimuli that evoked sustained changes in resting membrane potential, input resistance, and membrane fluctuations robustly modulated neuronal gain. The magnitude of gain modulation depended critically on the spatiotemporal properties of the visual stimulus. Gain modulation in vivo may thus be determined on a moment-to-moment basis by sensory context and the consequent dynamics of synaptic activation.

Nested clade analysis: an extensively validated method for strong phylogeographic inference

Petit (2007) speculates that three papers (Knowles, Maddison, 2002; Panchal, Beaumont, 2007; Petit, Grivet, 2002) have delivered the coup de grâce for nested clade phylogeographic analysis (NCPA). As Petit (2007) notes, NCPA is one of the most frequently used analytical tools in the area of phylogeography, so this speculation must be evaluated carefully.

Blinking Patterns and Corneal Staining

To investigate the blinking patterns of healthy subjects and soft contact lens wearers and determine whether these blinking characteristics were associated with corneal fluorescein staining. Fifteen young soft contact lens wearers and 11 young, healthy subjects participated in the study. The subjects were selected to have no significant eyelid disease. High-speed filming (100 frames per second) was used to capture the natural blinking patterns of the subjects for approximately 3 minutes. Custom written software was used to measure the vertical palpebral aperture at the start and the end of the downward motion of the upper eyelid. The vertical gap between the lids at the lowest point of the upper lid movement during each blink was measured (closed palpebral aperture). Corneal fluorescein staining was quantified on a 0-to-4 scale for each subject. Closed palpebral apertures in the healthy and soft contact lens-wearing subjects showed a wide distribution, with 22% of blinks being incomplete (<2/3 open aperture) in both groups of subjects. In soft contact lens wearers, there was a significant correlation (r = 0.40, P<0.05) between the mean closed palpebral aperture and the grade of corneal staining (primarily located inferiorly). The healthy subjects did not show the same degree of correlation (r = 0.16, P>0.1). However, the distribution of closed palpebral apertures was significantly different between those subjects with corneal staining compared to those without corneal staining (Kolmogorov-Smirnov two-sample test, healthy subjects with P=0.002 and soft lens wearers with P<0.001). The distribution of closed palpebral apertures of healthy and soft contact lens-wearing subjects showed no clear distinction between complete and incomplete blinks. Both groups of subjects show evidence of an association between the mean closed palpebral aperture size (degree of incomplete blinking) and the grade of corneal fluorescein staining, but the association is stronger in soft contact lens wearers.

Behavior therapy in dissociative convulsions disorder.

To compare the remission in symptoms achieved with behavior therapy and routine clinical care to that with routine clinical care given alone to patients having dissociative disorder. A randomized controlled trial. Psychiatry Unit, Lady Reading Hospital, Peshawar from April 2004 to September 2004. A total sample of 100 patients was recruited through Psychiatric OPD and Emergency unit. Patients were randomly allocated to the intervention or control group. The number of fits were recorded each day during admission. The patients were followed-up for four weeks after discharge. Hospital anxiety and depression scale and clinical global impression scales were applied. The two-sample Kolmogorov-Smirnov test was used to show the differences in relative frequencies of fits between the two groups. There were no statistically significant differences in sociodemographic and clinical variables in the intervention and control groups at baseline. There was a highly significant difference between the two groups in frequency of fits at discharge, on the first follow-up and on the fourth follow-up (p=0.000). Similarly, patients in the intervention group showed more improvement on hospital anxiety and depression scale compared to the control group, (p=0.000) at the end of four weeks. Behavioral intervention in the management of conversion disorder is more effective than the methods applied in our daily practice.

Comparability of five analytical systems for the determination of triiodothyronine, thyroxine and thyroid-stimulating hormone

The purpose of an external quality assessment (EQA) is to evaluate the analytical capability of clinical laboratories, identify differences among the laboratories and improve analytical quality. Our EQA results show that the rates of unsatisfactory performance for thyroid hormone tests were the highest in all of our EQA programs. Therefore, the main purpose of this study was to investigate unsatisfactory results by comparing the analytical values of five routinely used analytical systems. The Kruskal-Wallis and two-sample Kolmogorov-Smirnov tests were used to identify analytical differences among and between analytical systems, respectively. The rates of significantly different results compared to the total number of analytical results were 81.1%, 64.5%, 93.3%, 50.0% and 56.7% for free triiodothyronine, total triiodothyronine, free thyroxine, total thyroxine and thyroid-stimulating hormone, respectively. Relatively large analytical differences between analytical systems were observed, especially when the analytical systems were used to measure free thyroid hormones.

Micro-scale distribution of some arthropods inhabiting a Mediterranean sandy beach in relation to environmental parameters

Abstract A study on the spatial distribution of two tenebrionids and an isopod species was conducted at a small extent. Two species of the genus Phaleria were chosen because of their sympatric distribution and apparently similar adaptations to the beach environment. These scavenger species were studied in association to Tylos europaeus. Distributions, both perpendicular and parallel to the shoreline, were studied simultaneously with a grid of 20 × 20 pitfall traps arranged at a distance of 1 m from each other. Faunal samples were collected at two different hours of the night and core samples of sand were taken next to each pitfall trap for successive laboratory analysis. An index of dispersion was applied to test for aggregation of all species and of environmental parameters on the total, across- and long-shore. Kolmogorov–Smirnov two-sample test was used to compare the distributions between species. Regression analyse were applied to evaluate relationships between environmental parameters and species distributions. The study showed that the distribution of Phaleria species and T. europaeus was scale-dependent. The species and the values of the environmental parameters showed aggregated distributions both across- and long-shore. Aggregations of each Phaleria species differed according to their resting and foraging phases. For all species, sand moisture and salinity were the most important parameters explaining distribution. Granulometric parameters were correlated with the choice of the resting areas of both Phaleria species, whereas the spatial distribution of T. europaeus was correlated to the distribution of the organic matter.

Elderly Herbal Supplement Users Less Satisfied with Medical Care than Nonusers

The purpose of the study was to examine differences between elderly herbal supplement users and nonusers with respect to their perceptions of the safety of supplements and their satisfaction with current medical care. The researchers interviewed 69 elderly persons from congregate meal sites in four Illinois counties to assess herbal supplement use, perceptions of herbal supplement safety, medical supervision of herbal supplement use, and satisfaction with medical care. Two-sample Kolmogorov-Smirnov tests compared both perceived safety of herbal supplements and satisfaction with medical care of supplement users and nonusers. Herbal supplement users were more likely to perceive supplements as safe and to be less satisfied with conventional medical care than nonusers. Some elderly persons do not inform physicians that they are using herbal supplements, thus increasing the risk for supplement misuse, toxicity, and drug-supplement interactions. It is important that physicians, dietetics professionals, and pharmacists inquire about and discuss herbal supplement use with elderly patients.

Trends of prevalence and pathological spectrum of head and neck cancers in North India

Head and neck neoplasia constitute one of the commonest cancers in India. Use of smokeless tobacco (Pan masala, Zarda etc.) is on the increase in North India, especially in Uttar Pradesh, and is responsible for the large majority of these tumours. To assess the patients' characteristics, yearly prevalence and histopathological subtypes of the head and neck neoplasia (excluding oral cavity) in Allahabad and surrounding regions. A retrospective study of 11 years from 1990 to 2000 was designed. Data was collected year-wise using the tumor registry data. All biopsies submitted for histopathology to the Pathology department were reviewed and analyzed for demographic data, site and diagnosis. The Kolmogorov-Smirnov Two-Sample Test was utilized to determine whether two distributions are the same. A total of 40559 biopsies were examined in the department, of which, lesions of the head and neck region, excluding the oral cavity, constituted 694 biopsies (409 males and 285 females). One hundred and forty-four malignant lesions were reported, 114 being males and 30 females. A comparison of the age-specific prevalence rates of cancer during the study period showed that the prevalence was highest in patients belonging to the 50-59 years age group and squamous cell carcinoma Grade II was the most prevalent type. On an average, 58 new biopsies per annum were received. Properly structured site-specific data like this can augment the National Cancer Registry Programme and is an essential indicator for the magnitude and the pattern of the cancer problem in India.