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Chi-square Statistics (chi-square + statistics)
Selected AbstractsEffectiveness of limited cone-beam computed tomography in the detection of horizontal root fractureDENTAL TRAUMATOLOGY, Issue 3 2009vanē Kamburo Root fractures were created in the horizontal plane in 18 teeth by a mechanical force and fragments were relocated. Another 18 intact teeth with no horizontal root fracture served as a control group. Thirty-six teeth were placed in the respective empty maxillary anterior sockets of a human dry skull in groups three by three. Intraoral radiographs were obtained in three different vertical views by utilizing Eastman Kodak E-speed film, CCD sensor, RVG 5.0 Trophy and a PSP sensor Digora, Optime. Cone beam CT images were taken with a unit (3D Accuitomo; J Morita MFG. Corp, Kyoto, Japan). Three dental radiologists separately examined the intraoral film, PSP, CCD and cone beam CT images for the presence of horizontal root fracture. Specificity and sensitivity for each radiographic technique were calculated. Kappa statistics was used for assessing the agreement between observers. Chi-square statistics was used to determine whether there were differences between the systems. Results were considered significant at P < 0.05. Cone beam CT images revealed significantly higher sensitivities (P < 0.05) than the intraoral systems between which no significant differences were found. Specificities did not show any statistically significant differences between any of the four systems. The kappa values for inter-observer agreement between observers (four pairs) ranged between 0.82,0.90 for the 3DX evaluations and between 0.63,0.71 for the different types of intraoral images. Limited cone beam CT, outperformed the two-dimensional intraoral, conventional as well as digital, radiographic methods in detecting simulated horizontal root fracture. [source] A Cross-Cultural Survey of Students' Expectations of Foreign Language TeachersFOREIGN LANGUAGE ANNALS, Issue 3 2003Article first published online: 31 DEC 200, Eri Banno One hundred ten Japanese, 98 American, and 105 Chinese college students chose five important qualities in good foreign language teachers from a list. Chi-square statistics and the Spearman rank-order correlation coefficient were used for the analyses. A statistically significant difference was found for some qualities. The results indicate that the students of all groups placed importance on some qualities, such as "explain clearly" and "approachable," and that Japanese and Chinese students had some similar expectations in foreign language teachers. Chinese participants placed more importance on pronunciation than did Japanese and Americans. Americans valued creative and patient teachers more than Japanese students did, whereas Japanese valued entertaining, impartial, open-minded, and reliable teachers more than Americans. [source] Bispectral Electroencephalographic Analysis of Patients Undergoing Procedural Sedation in the Emergency DepartmentACADEMIC EMERGENCY MEDICINE, Issue 6 2003James R. Miner MD Abstract Objective: To determine whether there is a correlation between the level of sedation achieved during procedural sedation (PS) in the emergency department as determined by bispectral electroencephalographic (EEG) analysis (BIS) and the rate of respiratory depression (RD), the patient's perception of pain, recall of the procedure, and satisfaction. Methods: This was a prospective observational study conducted in an urban county hospital of adult patients undergoing PS using propofol, methohexital, etomidate, and the combination of fentanyl and midazolam. Consenting patients were monitored by vital signs, pulse oximetry, nasal-sample end-tidal carbon dioxide (ETCO2), and BIS monitors during PS. Respiratory depression (RD) was defined as an oxygen saturation <90%, a change from baseline ETCO2 of >10 mm Hg, or an absent ETCO2 waveform at any time during the procedure. After the procedure, patients were asked to complete three 100-mm visual analog scales (VASs) concerning their perception of pain, recall of the procedure, and satisfaction with the procedure. Patients were divided into four groups based on the lowest BIS score recorded during the procedure, group 1, >85; group 2, 70,85; group 3, 60,69; group 4, <60. Rates of RD and VAS outcomes were compared between groups using chi-square statistics. Results: One hundred eight patients were enrolled in the study. No serious adverse events were noted. RD was seen in three of 14 (21.4%) of the patients in group 1, seven of 34 (20.6%) in group 2, 16 of 26 (61.5%) in group 3, and 18 of 34 (52.9%) in group 4. The rate of RD in patients in group 2 was not significantly different from that in group 1 (p = 0.46). The rate of RD in group 2 was significantly lower than that in groups 3 (p = 0.0003) and 4 (p = 0.006). For the VAS data, when group 1 was compared with the combined groups 2, 3, and 4, it had significantly higher rates of pain (p = 0.003) and recall (p = 0.001), and a dissatisfaction rate (p = 0.085) that approached significance. When groups 2, 3, and 4 were compared with chi-square test, there was not a significant difference in pain (p = 0.151), recall (p = 0.27), or satisfaction (p = 0.25). Conclusions: Patients with a lowest recorded BIS score between 70 and 85 had the same VAS outcomes as more deeply sedated patients and the same rate of RD as less deeply sedated patients. This range of scores represented the optimally sedated patients in this study. [source] Incidence of Traumatic Lumbar PunctureACADEMIC EMERGENCY MEDICINE, Issue 2 2003Kaushal H. Shah MD Abstract Objective: To determine the incidence of traumatic lumbar puncture (LP). Methods: A retrospective study was conducted at an urban, university tertiary care referral center with 50,000 annual emergency department (ED) visits. The study population included all patients who had cerebrospinal fluid (CSF) samples sent to the laboratory between August 15, 2000, and August 14, 2001. The numbers of red blood cells (RBCs) recorded in the first and last CSF tubes, the location where the LP was performed, and the discharge summary and the discharge diagnoses from the particular visit were obtained. All patients with intracranial pathology and CSF obtained via neurosurgical procedure or fluoroscopic guidance were excluded from the study group. Given no clear definition of traumatic LP in the literature, the incidence of traumatic LP was calculated using a cutoff of greater than 400 RBCs (visual threshold for bloody fluid) and 1,000 RBCs (arbitrary threshold selected by other authors) in CSF tube 1. Proportions were compared using chi-square statistics. Results: Seven hundred eighty-six CSF samples were recorded over one year. Twenty-four samples were obtained from patients with intracranial pathology or were obtained via a neurosurgical procedure. Of the remaining 762 CSF samples in the study population, 119 (15.6%) were traumatic using a cutoff of 400 RBCs, and 80 (10.5%) were traumatic, using a cutoff of 1,000 RBCs in tube 1. Five hundred three LPs were done in the ED and 259 were attributed to all other locations in the hospital. Using a cutoff of 400 RBCs, the incidence of traumatic LP in the ED was 13.3%, compared with 20% in the rest of the hospital (p < 0.025). Similarly, using a cutoff of 1,000 RBCs, the incidence of traumatic LP in the ED was 8.9%, compared with 13.5% in the rest of the hospital (p = 0.1). The incidence of "champagne taps" (defined as zero RBCs in the first and last tubes) in the ED was 34.4%, compared with 24.3% in the rest of the hospital (p < 0.01). Conclusions: The incidence of traumatic lumbar puncture is approximately 15% using a cutoff of 400 RBCs and 10% using a cutoff of 1,000 RBCs. In this study, the rate of traumatic lumbar puncture was significantly less (with a cutoff of 400 RBCs) and the rate of champagne tap was significantly greater for LPs done in the ED compared with the rest of the hospital. [source] BRIEF REPORT: No association of alcohol dependence with SLC6A5 and SLC6A9 glycine transporter polymorphismsADDICTION BIOLOGY, Issue 4 2009Gabriele Koller ABSTRACT To determine whether glycine transporter polymorphisms are associated with alcoholism, three genetic variants of SLC6A5 and two polymorphisms of SLC6A9 were genotyped in 463 German non-alcoholic controls and 644 German alcohol-dependent subjects. Association was investigated employing chi-square statistics and haplotype analysis. There was a significant association between the SLC6A5 polymorphism (rs1443547) and alcohol dependence as alcoholic individuals had a lower rate of AG-allele (,2 = 6.048, P = 0.049, d.f. = 2), which did not remain significant after correction for multiple testing. There was no association between SLC6A9 glycine transporter polymorphisms and alcohol dependence, and also none in haplotype analysis. [source] Centralizing the non-central chi-square: a new method to correct for population stratification in genetic case-control association studiesGENETIC EPIDEMIOLOGY, Issue 4 2006Prakash Gorroochurn Abstract We present a new method, the ,-centralization (DC) method, to correct for population stratification (PS) in case-control association studies. DC works well even when there is a lot of confounding due to PS. The latter causes overdispersion in the usual chi-square statistics which then have non-central chi-square distributions. Other methods approach the non-centrality indirectly, but we deal with it directly, by estimating the non-centrality parameter , itself. Specifically: (1) We define a quantity ,, a function of the relevant subpopulation parameters. We show that, for relatively large samples, , exactly predicts the elevation of the false positive rate due to PS, when there is no true association between marker genotype and disease. (This quantity , is quite different from Wright's FST and can be large even when FST is small.) (2) We show how to estimate ,, using a panel of unlinked "neutral" loci. (3) We then show that ,2 corresponds to , the non-centrality parameter of the chi-square distribution. Thus, we can centralize the chi-square using our estimate of ,; this is the DC method. (4) We demonstrate, via computer simulations, that DC works well with as few as 25,30 unlinked markers, where the markers are chosen to have allele frequencies reasonably close (within ±.1) to those at the test locus. (5) We compare DC with genomic control and show that where as the latter becomes overconservative when there is considerable confounding due to PS (i.e. when , is large), DC performs well for all values of ,. Genet. Epidemiol. 2006. © 2006 Wiley-Liss, Inc. [source] Statistical power when testing for genetic differentiationMOLECULAR ECOLOGY, Issue 10 2001N. Ryman Abstract A variety of statistical procedures are commonly employed when testing for genetic differentiation. In a typical situation two or more samples of individuals have been genotyped at several gene loci by molecular or biochemical means, and in a first step a statistical test for allele frequency homogeneity is performed at each locus separately, using, e.g. the contingency chi-square test, Fisher's exact test, or some modification thereof. In a second step the results from the separate tests are combined for evaluation of the joint null hypothesis that there is no allele frequency difference at any locus, corresponding to the important case where the samples would be regarded as drawn from the same statistical and, hence, biological population. Presently, there are two conceptually different strategies in use for testing the joint null hypothesis of no difference at any locus. One approach is based on the summation of chi-square statistics over loci. Another method is employed by investigators applying the Bonferroni technique (adjusting the P -value required for rejection to account for the elevated alpha errors when performing multiple tests simultaneously) to test if the heterogeneity observed at any particular locus can be regarded significant when considered separately. Under this approach the joint null hypothesis is rejected if one or more of the component single locus tests is considered significant under the Bonferroni criterion. We used computer simulations to evaluate the statistical power and realized alpha errors of these strategies when evaluating the joint hypothesis after scoring multiple loci. We find that the ,extended' Bonferroni approach generally is associated with low statistical power and should not be applied in the current setting. Further, and contrary to what might be expected, we find that ,exact' tests typically behave poorly when combined in existing procedures for joint hypothesis testing. Thus, while exact tests are generally to be preferred over approximate ones when testing each particular locus, approximate tests such as the traditional chi-square seem preferable when addressing the joint hypothesis. [source] Trace Metals' Abnormalities in Hemodialysis Patients: Relationship with MedicationsARTIFICIAL ORGANS, Issue 11 2000Su-Hui Lee Abstract: A multicenter collaborative study was performed to investigate the prevalence of abnormal blood contents of 6 trace metals, copper (Cu), zinc (Zn), aluminum (Al), lead (Pb), cadmium (Cd), and mercury (Hg), in hemodialysis (HD) patients and to analyze their relationship with the medications, such as CaCO3, Ca acetate, Al containing phosphate-binding agents, 1,25-dihydroxy vitD3, 1-hydroxy vitD3, and erythropoietin (EPO), as well as hematocrit level, by chi-square statistics. From 6 medical centers in Taiwan, we included 456 patients in maintenance HD for more than 4 months for this study, and they had continued the previously mentioned medications for at least 3 months. Blood samples were collected before initiating HD, and atomic absorption spectrophotometry was used to measure plasma levels of Cu, Zn, and Al as well as whole blood levels of Pb, Cd, and Hg. Three hundred seventy-five (78%) of the HD patients had low plasma Zn levels, that is, <800 ,g/L, and the mean (±SD) concentration was 705.8 (±128.23) ,g/L in all subjects. One hundred forty-one (31%) of the HD patients had high plasma Al, that is, >50 ,g/L, and the mean (±SD) was 44.30 (±28.28) ,g/L in all subjects. Three hundred thirty-three (73%) of the dialysis patients had high Cd levels, that is, >2.5 ,g/L, and the mean (±SD) was 3.32 (±1.49) ,g/L in all subjects. The majority of HD patients had normal blood levels of Cu, PB, and Hg. Only 21 (4.6%), 5 (1.1%), and 3 (0.06%) patients had elevated blood levels of Cu, Pb, and Hg, respectively. Their mean (±SD) blood concentration of Cu, Pb, and Hg were 1,049.78 (±233.25) ,g/L, 7.45 (±3.95) ,g/dL, and 3.17 (±25.56) ,g/L, respectively. Three patients had elevated plasma Hg concentrations, that is, 546, 12.6, and 24.0 ,g/L, respectively. In the 152 normal healthy age and sex matched control group, the blood levels of Al, Cd, and Pb were all significantly lower than the HD patients. However, the levels of Cu and Zn were higher in the control group. The Hg level was not significantly different in both groups. There was no statistical difference between patients with normal and abnormal blood levels of trace metals in various medications except Al containing phosphate binder. The Al containing phosphate binder users had significantly higher plasma Al levels (54.71 ± 26.70 versus 41.15 ± 28.03 ,g/L, p < 0.001) and hematocrit levels (29.61 ± 4.61 versus 27.81 ± 3.91, p < 0.0005). There was no statistical correlation between erythropoietin (EPO) dose and hematocrit level in these patients. In conclusion, the blood level of trace metals of these HD patients except Al was not related to their medications. However, caution must be exercised in interpreting this result as dose and duration of medication; efficiency of HD and water treatment may play an important role. Otherwise, environmental factors, diet, and the aging process may contribute to the trace metal burden in uremia. Thus, Zn and Cu are abundant in seafood, and Cd is abundant in contaminated plants such as rice. [source] Physical performance limitations among adult survivors of childhood brain tumorsCANCER, Issue 12 2010Kirsten K. Ness PhD Abstract BACKGROUND: Young adult survivors of childhood brain tumors (BTs) may have late effects that compromise physical performance and everyday task participation. The objective of this study was to evaluate muscle strength, fitness, physical performance, and task participation among adult survivors of childhood BTs. METHODS: In-home evaluations and interviews were conducted for 156 participants (54% men). Results on measures of muscle strength, fitness, physical performance, and participation were compared between BT survivors and members of a population-based comparison group by using chi-square statistics and 2-sample t tests. Associations between late effects and physical performance and between physical performance and participation were evaluated in regression models. RESULTS: The median age of BT survivors was 22 years (range, 18-58 years) at the time of the current evaluation, and they had survived for a median of 14.7 years (range, 6.5-45.9 years) postdiagnosis. Survivors had lower estimates of grip strength (women, 24.7 ± 9.2 kg vs 31.5 ± 5.8 kg; men, 39.0 ± 12.2 kg vs 53.0 ± 10.1 kg), knee extension strength (women, 246.6 ± 95.5 Newtons [N] vs 331.5 ± 5.8 N; men, 304.7 ± 116.4 N vs 466.6 ± 92.1 N), and peak oxygen uptake (women, 25.1 ± 8.8 mL/kg per minute vs 31.3 ± 5.1 mL/kg per minute; men, 24.6 ± 9.5 mL/kg per minute vs 33.2 ± 3.4 mL/kg per minute) than members of the population-based comparison group. Physical performance was lower among survivors and was associated with not living independently (odds ratio [OR], 5.0; 95% confidence interval [CI], 2.0-12.2) and not attending college (OR, 2.3; 95% CI 1.2-4.4). CONCLUSIONS: Muscle strength and fitness values among BT survivors were similar to those among individuals aged ,60 years and were associated with physical performance limitations. Physical performance limitations were associated with poor outcomes in home and school environments. The current data indicated an opportunity for interventions targeted at improving long-term physical function in this survivor population. Cancer 2010. © 2010 American Cancer Society. [source] Screening mammography performance and cancer detection among black women and white women in community practiceCANCER, Issue 1 2004Karminder S. Gill M.S.P.H. Abstract BACKGROUND Despite improvement in mammography screening attendance, black women continue to have poorer prognosis at diagnosis than white woman. Data from the Carolina Mammography Registry were used to evaluate whether there may be differences in mammography performance or detected cancers when comparing black women with white women who are screened by mammography. METHODS Prospectively collected data from community-based mammography facilities on 468,484 screening mammograms (79,397 in black women and 389,087 in white women) were included for study. Mammograms were linked to a pathology data base for identification of cancers. Sensitivity, specificity, positive predictive value, and cancer detection rates were compared between black women and white women. Logistic regression methods were used to control for covariates associated with performance characteristics. Differences in cancer characteristics were compared between black women and white women using chi-square statistics. RESULTS Screening mammography performance results for black women compared with white women were as follows: sensitivity, odds ratio (OR) = 1.07 (95% confidence interval [95% CI], 0.83,1.39); specificity, OR = 1.02 (95% CI, 0.98,1.06); and positive predictive value, OR = 1.07 (95% CI, 0.94,1.23). Among women with no previous screening, black women had a larger proportion of invasive tumors that measured , 2 cm (38% vs. 26%; P = 0.04). The cancer detection rate was highest among black women who reported symptoms at screening (13.9 per 1000 black women vs. 7.9 per 1000 white women). Invasive cancers in black women were poorer grade (P = 0.001), and more often had negative estrogen receptor status and progesterone receptor status (P < 0.001). CONCLUSIONS Overall, screening mammography performed equally well in black women and white women controlling for age, breast density, and time since previous mammogram. Black women who reported symptoms had larger and higher grade tumors compared with white women. Educational efforts need to be strengthened to encourage black women to react sooner to symptoms, so that the tumors detected will be smaller and black women will have a better prognosis when they appear for mammography. Cancer 2004;100:139,48. © 2003 American Cancer Society. [source] | |||||||||||||