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Pearson's Test (pearson + test)

Distribution by Scientific Domains

Medical Sciences	42%
Life Sciences	42%

Selected Abstracts

Pearson's Test, Trend Test, and MAX Are All Trend Tests with Different Types of Scores

ANNALS OF HUMAN GENETICS, Issue 2 2009
Gang Zheng
Summary Pearson's test is one of the most commonly used statistics for testing genetic association of case-control data. The trend test is another one which assumes a dose-response model between the risk of the disease and genotypes. To apply the trend test, a set of ordered scores is assigned a priori based on the underlying genetic model. Pearson's test is model-free and robust, but is less powerful for common genetic models. MAX is another robust test statistic, which takes the maximum of the trend tests over a family of scientifically plausible genetic models. We show that the three test statistics are all trend tests but with different types of scores; whether the scores are prespecified or data-driven, or whether the scores are ordered (restricted) or not ordered (unrestricted). We then provide insights into power performance of the three tests when the underlying genetic model is unknown and discuss which test to use for the analyses of case-control genetic association studies. [source]

Parents and Practitioners Are Poor Judges of Young Children's Pain Severity

ACADEMIC EMERGENCY MEDICINE, Issue 6 2002
Adam J. Singer MD
Objective: Visual analog pain scales are reliable measures in older children and adults; however, pain studies that include young children often rely on parental or practitioner assessments for measuring pain severity. The authors correlated patient, parental, and practitioner pain assessments for young children with acute pain. Methods: This was a prospective, descriptive study of a convenience sample of 63 emergency department patients aged 4-7 years, with acute pain resulting from acute illness or painful invasive procedures. A trained research assistant administered a structured pain survey containing demographic and historical features to all parents/guardians. Children assessed their pain severity using a validated ordinal scale that uses five different faces with varying degrees of frowning (severe pain) or smiling (no pain). Each face was converted to a numeric value from 0 (no pain) to 4 (severe pain). Parents and practitioners independently assessed their child's pain using a validated 100-mm visual analog scale (VAS) marked "most pain" at the high end. Pairwise correlations between child, parent, and practitioner pain assessments were performed using Spearman's or Pearson's test as appropriate. The association between categorical data was assessed using ,2 tests. Results: Sixty-three children ranging in age from 4 to 7 were included. Mean age (±SD) was 5.7 (±1.1); 42% were female. Fifty-seven successfully completed the face scale. The distribution of the children's scores was 0-17%, 1-9%, 2-30%, 3-14%, and 4-30%. Mean parental and practitioner scores (±SD) on the VAS were 61 (±26) mm and 37 (±26) mm, respectively (maximal = 100 mm). Correlation between child and parent scores was 0.47 (p < 0.001). Correlation between child and practitioner scores was 0.08 (p = 0.54). Correlation between parent and practitioner scores was 0.04 (p = 0.001). Conclusions: There is poor agreement between pain ratings by children, parents, and practitioners. It is unclear which assessment best approximates the true degree of pain the child is experiencing. [source]

Estimation of P -value of MAX test with double triangle diagram for 2 × 3 SNP case-control tables

GENETIC EPIDEMIOLOGY, Issue 6 2010
Katsura Hirosawa
Abstract Single nucle otide polymorphisms (SNPs) are the most popular markers in genetic epidemiology. Multiple tests have been applied to evaluate genetic effect of SNPs, such as Pearson's test with two degrees of freedom, three tests with one degree of freedom (,2 tests for dominant and recessive modes and Cockran-Armitage trend test for additive mode) as well as MAX3 test and MAX test, which are combination of four tests mentioned earlier. Because MAX test is a combination of Pearson's test of two degrees of freedom and two tests of one degree of freedom, the probability density function (pdf) of MAX statistics does not match pdf of ,2 distribution of either one or two degrees of freedom. In order to calculate P -value of MAX test, we introduced a new diagram, Double Triangle Diagram, which was an extension of de Finetti diagram in population genetics which characterized all of the tests for 2 × 3 tables. In the diagram the contour lines of MAX statistics were consisted of elliptic curves and two tangent lines to the ellipses in the space. We normalized the ellipses into regular circles and expressed P -value of MAX test in an integral form. Although a part of the integral was not analytically solvable, it was calculable with arbitrary accuracy by dividing the area under pdf into finite rectangles. We confirmed that P -values from our method took uniform distribution from 0 to 1 in three example marginal count sets and concluded that our method was appropriate to give P -value of MAX test for 2 × 3 tables. Genet. Epidemiol. 34:543,551, 2010. © 2010 Wiley-Liss, Inc. [source]

New method of dynamic color doppler signal quantification in metastatic lymph nodes compared to direct polarographic measurements of tissue oxygenation

INTERNATIONAL JOURNAL OF CANCER, Issue 6 2005
Thomas Scholbach
Abstract Tumor growth depends on sufficient blood and oxygen supply. Hypoxia stimulates neovascularization and is a known cause for radio- and chemoresistance. The objective of this study was to investigate the use of a novel ultrasound technique for the dynamic assessment of vascularization and oxygenation in metastatic lymph nodes. Twenty-four patients (age 44,78 years) with cervical lymph node metastases of squamous cell head and neck cancer were investigated by color duplex sonography and 17 (age 46,78 years) were investigated additionally with polarography. Sonography was performed after contrast enhancer infusion under defined conditions. Intranodal perfusion data (color hue, colored area) were measured automatically by a novel software technique. This allows an evaluation of blood flow dynamics by calculating perfusion intensity,velocity, perfused area, as well as the novel parameters tissue resistance index (TRI) and tissue pulsatility index (TPI),for each point of a complete heart cycle. Tumor tissue pO2 was measured by means of polarographic needle electrodes placed intranodally. The sonographic and polarographic data were correlated using Pearson's test. Sonography demonstrated a statistically significant inverse correlation between hypoxia and perfusion and significant TPI and TRI changes with different N-stages. The percentage of nodal fraction with less than 10 mmHg oxygen saturation was significantly inversely correlated with lymph node perfusion (r = ,0.551; p = 0.021). Nodes with a perfusion of less than 0.05 cm/sec flow velocity showed significantly larger hypoxic areas (p = 0.006). Significant differences of TPI and TRI existed between nodes in stage N1 and N2/N3 (p = 0.028 and 0.048, respectively). This new method of dynamic signal quantification allows a noninvasive and quantitative assessment of tumor and metastatic lymph node perfusion by means of commonly available ultrasound equipment. © 2004 Wiley-Liss, Inc. [source]

Pearson's Test, Trend Test, and MAX Are All Trend Tests with Different Types of Scores

A Robust Genome-Wide Scan Statistic of the Wellcome Trust Case,Control Consortium

BIOMETRICS, Issue 4 2009
Jungnam Joo
Summary In genome-wide association (GWA) studies, test statistics that are efficient and robust across various genetic models are preferable, particularly for studying multiple diseases in the Wellcome Trust Case,Control Consortium (WTCCC, 2007,,Nature,447, 661,678). A new test statistic, the minimum of the p-values of the trend test and Pearson's test, was considered by the WTCCC. It is referred to here as MIN2. Because the minimum of two p-values is no longer a valid p-value itself, the WTCCC only used it to rank single nucleotide polymorphisms (SNPs) but did not report the p-values of the associated SNPs when MIN2 was used for ranking. Given its importance in practice, we derive the asymptotic null distribution of MIN2, study some of its analytical properties related to GWA studies, and compare it with existing methods (the trend test, Pearson's test, MAX3, and the constrained likelihood ratio test [CLRT]) by simulations across a wide range of possible genetic models: the recessive (REC), additive (ADD), multiplicative (MUL), dominant (DOM), and overdominant models. The results show that MAX3 and CLRT have greater efficiency robustness than other tests when the REC, ADD/MUL, and DOM models are possible, whereas Pearson's test and MIN2 have greater efficiency robustness if the possible genetic models also include the overdominant model. We conclude that robust tests (MAX3, MIN2, CLRT, and Pearson's test) are preferable to a single trend test for initial GWA studies. The four robust tests are applied to more than 100 SNPs associated with 11 common diseases identified by the two WTCCC GWA studies. [source]

Optimal microvessel density from composite graft of autogenous maxillary cortical bone and anorganic bovine bone in sinus augmentation: influence of clinical variables

CLINICAL ORAL IMPLANTS RESEARCH, Issue 2 2010
Pablo Galindo-Moreno
Abstract Objectives: The objectives of this study were to assess the microvessel density (MVD) of intra-sinus grafts after 6 months of wound healing and to study the relationship between revascularization processes and patient clinical variables and habits. Material and methods: We performed 45 maxillary sinus augmentations with different implant placements in 25 consecutive patients, obtaining bone cores of the grafted area for histological, histomorphometric and immunohistochemical study. Biopsies were also taken from pristine bone in the posterior maxilla (control). Results: All implants survived at 24 months. Biopsies of sinus augmentation areas showed significantly greater remodeling activity vs. pristine bone, with significantly more osteoid lines. The morphometry study revealed 34.88±15.2% vital bone, 32.02±15.1% non-mineralized tissue and 33.08±25.4% remnant anorganic bovine bone particles. The number of CD34-positive vessels was 86.28±55.52/mm2 in graft tissue vs. 31.52±13.69/mm2 in native tissue (P=0.002, Mann,Whitney U=46). The larger amount of non-mineralized tissue in grafts was directly correlated with a higher MVD (r=0.482, P=0.0001, Pearson's test). MVD was affected by the presence of periodontitis or tobacco and alcohol consumption. Conclusion: The angiogenesis and revascularization obtained by this type of graft achieve adequate tissue remodeling for osseointegration and are influenced by periodontal disease and tobacco or alcohol consumption. To cite this article: Galindo-Moreno P, Padial-Molina M, Fernández-Barbero JE, Mesa F, Rodríguez-Martínez D, O'Valle F. Optimal microvessel density from composite graft of autogenous maxillary cortical bone and anorganic bovine bone in sinus augmentation: influence of clinical variables. Clin. Oral Impl. Res. 21, 2010; 221,227 doi: 10.1111/j.1600-0501.2009.01827.x [source]