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Principal Factor Analysis (principal + factor_analysis)
Selected AbstractsFactor analysis of spectroelectrochemical reduction of FAD reveals the pKa of the reduced state and the reduction pathwayJOURNAL OF CHEMOMETRICS, Issue 12 2007Edmund R. Malinowski Abstract The free flavin adenine dinucleotide (FAD) cofactor is known to exhibit a pH-dependent midpoint potential involving a simultaneous two-electron transfer step (n,=,2). Uv-vis spectroelectrochemical reductions of FAD at constant pH, ranging from 5 to 9, were recorded and analyzed by factor analysis. Principal factor analysis was used to determine the number of species present at each pH. The results indicate that only two composite forms of FAD are present: the oxidized and the reduced forms. Window factor analysis was used to extract the concentration profiles of the controlling species. The oxidized form was found to be a single pH-independent species, whereas the reduced form consists of two species. The pH-dependent spectroscopic changes of reduced FAD were best modeled by a single proton transfer step involving two different ionization states with an apparent pKa,=,6.3. This value compares favorably with those obtained from NMR and from midpoint potential measurements. At pH 6, the reduction of FAD was found to be first order, whereas at pH 9 the reduction is zero order; these observations are explained in terms of the reaction pathway involving xanthine oxidase, its substrate, and the pH. Copyright © 2007 John Wiley & Sons, Ltd. [source] Psychometric evaluation of a measure of Beck's negative cognitive triad for youth: applications for African,American and Caucasian adolescentsDEPRESSION AND ANXIETY, Issue 4 2005Leilani Greening Abstract A measure of Beck's negative cognitive triad, the Cognitive Triad for Children (CTI-C), was evaluated for its psychometric properties and utility with a community sample of 880 African,American and Caucasian adolescents. High-school students ranging from 14 to 17 years of age completed the CTI-C, the Children's Depression Inventory (CDI) and the Children's Attributional Style Questionnaire-Revised (CASQ-R) on two occasions 4 months apart. The CTI-C was found to be internally consistent, Cronbach's ,=.90, to have acceptable test-retest reliability, r=.70, and concurrent validity as demonstrated by a significant correlation with the CASQ-R, r=.53. A principal factor analysis with promax rotation did not yield support for Beck's tripartite model of negative cognitions about the self, world, and future but rather yielded three factors with a combination of cognitions from all three domains. African American adolescents who reported more maladaptive cognitions on the CTI-C reported fewer depressive symptoms on the CDI 4 months later compared to their Caucasian counterparts, suggesting some limitation to using the CTI-C to predict depressive symptoms in African,American youth; however, Factor 1 derived from a factor analysis with the sample was more consistent in predicting future symptoms among both African,American and Caucasian adolescents. This factor consisted largely of positively worded items, offering some support for low positive affect as a predictor of depressive symptoms in adolescents. Depression and Anxiety 21:161,169, 2005. © 2005 Wiley-Liss, Inc. [source] A statistical downscaling method for monthly total precipitation over TurkeyINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2004Hasan Tatli Abstract Researchers are aware of certain types of problems that arise when modelling interconnections between general circulation and regional processes, such as prediction of regional, local-scale climate variables from large-scale processes, e.g. by means of general circulation model (GCM) outputs. The problem solution is called downscaling. In this paper, a statistical downscaling approach to monthly total precipitation over Turkey, which is an integral part of system identification for analysis of local-scale climate variables, is investigated. Based on perfect prognosis, a new computationally effective working method is introduced by the proper predictors selected from the National Centers for Environmental Prediction,National Center for Atmospheric Research reanalysis data sets, which are simulated as perfectly as possible by GCMs during the period of 1961,98. The Sampson correlation ratio is used to determine the relationships between the monthly total precipitation series and the set of large-scale processes (namely 500 hPa geopotential heights, 700 hPa geopotential heights, sea-level pressures, 500 hPa vertical pressure velocities and 500,1000 hPa geopotential thicknesses). In the study, statistical preprocessing is implemented by independent component analysis rather than principal component analysis or principal factor analysis. The proposed downscaling method originates from a recurrent neural network model of Jordan that uses not only large-scale predictors, but also the previous states of the relevant local-scale variables. Finally, some possible improvements and suggestions for further study are mentioned. Copyright © 2004 Royal Meteorological Society [source] Assessment of patient satisfaction with pharmaceutical services in a Nigerian teaching hospitalINTERNATIONAL JOURNAL OF PHARMACY PRACTICE, Issue 1 2004Azuka C. Oparah lecturer ABSTRACT Objective To assess patients' satisfaction with pharmaceutical services using an"ideal referent" model, and to further explore the validity of an existing patient satisfaction instrument. Method A cross-sectional survey was conducted with a sample of 500 outpatients recruited consecutively at the University of Benin teaching hospital, Nigeria. A self-completion questionnaire that employed a Likert-type scale was used. Data were used to calculate scores on a scale that ranged from 20 to 100, with an assumed midpoint of 60. Descriptive statistics on the sample characteristics and questionnaire items were computed including means, standard deviations and frequency distributions. Varimax rotation with Kaiser normalisation was employed in principal factor analysis. Student's t -test and one-way ANOVA were used for inferential statistics. Key findings The instrument reliability was determined to be 0.9641 and was comparable to the reference study. Nearly half of the patients (46%) rated the amount of time the pharmacist offered to spend with them as poor. About one-third rated promptness of prescription service as poor. Only 49% felt satisfied with the pharmaceutical services. Overall, pharmacy services received a satisfaction rating of 56.04±24.49, below the midpoint. Perceived satisfaction was significantly higher in "friendly explanation" than in "managing therapy" (t=3.916; P<0.0001). Conclusion The study provides evidence that patients experience low satisfaction with current pharmaceutical services at the study hospital. The sociodemographic characteristics of patients were not associated with their level of satisfaction. We further confirm the validity of the patient satisfaction questionnaire in a Nigerian practice setting. [source] Ecological niche specialization inferred from morphological variation and otolith strontium of Arctic charr Salvelinus alpinus L. found within open lake systems of southern Baffin Island, Nunavut, CanadaJOURNAL OF FISH BIOLOGY, Issue 6 2009T. N. Loewen The presence of two morphotypes of Arctic charr Salvelinus alpinus was confirmed via morphological variation and otolith strontium (Sr) within three open-lake systems of southern Baffin Island, Nunavut, Canada: Qinngu (LH001), Iqalugaarjuit Lake (PG082) and Qasigiat (PG015). Analysis of otolith Sr indicates that a component of each S. alpinus population within lakes LH001 and PG082 is migratory (large,maturing S. alpinus), whereas another component is lake-resident (small,maturing S. alpinus). Alternatively, small and large maturing S. alpinus may both inhabit tidal habitats during their lifetime in lake PG015. Three morphological characters were identified by principal factor analysis (PFA) as characters that were different between maturity groups for all lakes studied: eye diameter, pectoral fin length and pelvic fin length. As well, upper jaw length (LH001 and PG082) and fork depth (PG015) were identified in PFA as traits that differed between morphs. Univariate tests of morphological characters identified by PFA demonstrated maturity group differences with the exception of eye diameter in Lake PG015 and upper jaw length and pelvic fin length in lake LH001. No difference was found in the MANOVA test of upper and lower gill raker number between small,maturing and undeveloped fish within all lakes studied. Clear morphological variation observed between small,maturing and undeveloped fish in all three lakes of the study suggests ecological niche separation between morphotypes. This is the first documented case of lake-resident S. alpinus use of the tidal habitat in the presence of a migratory large,maturing morphotype. [source] Factor Structure and Concurrent Validity of the Obsessive Compulsive Drinking Scale in a Group of Alcohol-Dependent Subjects of Mexico CityALCOHOLISM, Issue 7 2009Marta Cordero Background:, Obsessive thoughts and compulsive drinking behaviors have been proposed as key factors associated with the loss of control over alcohol consumption experienced by alcohol-dependent patients. The self-report 14-item Obsessive Compulsive Drinking Scale (OCDS; Anton et al., 1995) was designed in order to rate these features. Methods:, A Spanish-translated version of the OCDS was applied to a group of 159 alcohol-dependent subjects while in abstinence, and data were analyzed in order to evaluate the factor structure and concurrent validity of the scale. Results:, Several solutions were explored after applying the principal factor analysis to the data. The most plausible result was obtained after excluding the items on quantity and frequency of drinking. This model explaining 56.9% of the variance included 2 factors: obsessive thoughts related to drinking and interference/behaviors related to drinking. Additionally, OCDS scores were significantly correlated with measures for the Alcohol Dependence Scale, number of DSM-IV criteria met for alcohol dependence as well as the number of days in a week engaged in heavy drinking, indicating concurrent validity. Conclusions:, Our results support the use of OCDS as a valid self-rated instrument that can be broadly applied in research and treatment settings. However, its current version includes questions that may not represent the core concept of craving. The abridged 12-item version of the scale (excluding the items on drinking habits) maintains good psychometrics features and seems to be adequate when different cognitive and behavioral dimensions are explored. [source] Reliability and validity of the Japanese version of the child abuse potential inventory abuse scaleASIA-PACIFIC PSYCHIATRY, Issue 3 2009Yoshiya Kawamura BE MD Abstract Introduction: The present study examined the reliability, validity, and cutoff scores of the Japanese version of the Child Abuse Potential Inventory (CAPI) abuse scale, which screens for parents at risk of child abuse. Methods: Samples consisted of 1,809 parents, 109 students, and 33 child abusers in Japan. The CAPI was administered to all participants, and twice to the student sample at a 2-week interval. Internal consistency was evaluated by Cronbach's ,, and construct validity by principal factor analysis with the parent sample. Test-retest reliability was assessed with Pearson's r with the student sample. With regard to predictive validity, the cutoff scores and classification rates were calculated through discriminant analysis between abusers and matched non-abusers. Results: Internal consistency (Cronbach's ,=0.88), test-retest reliability (Pearson's r=0.93; two-tailed P<0.001), and predictive validity (overall diagnostic power=90%) were all highly satisfactory. Regarding construct validity, the six-factor structure of the original version was not replicated; only three factors were obtained. The discriminant analysis showed the basic cutoff score as 159. The conservative cutoff score for the upper 5% of the parent sample was 218. Discussion: The Japanese version of the CAPI abuse scale showed highly satisfactory internal consistency, test-retest reliability, and predictive validity. The construct correspondence with the original version was more compromised. This version of the CAPI identified parents with scores of 159 or greater as being at risk of abusing a child. [source] Measuring Nausea in Emergency Department Patients via the Use of Exploratory Factor AnalysisACADEMIC EMERGENCY MEDICINE, Issue 6 2010Robert L. Cloutier MD Abstract Objectives:, The objective was to evaluate the applicability of a previously studied multifactorial nausea scale in the emergency department (ED) setting via exploratory factor analysis (EFA). Methods:, Two studies evaluated the validity and factor structure of 18 nausea descriptors scored on 11-point Likert scales. Trained research volunteers administered the scale to 83 men and 123 women in the first sample and to 100 men and 230 women in the second sample. All patients were assessed at enrollment and again at 90 minutes to detect changes in symptom severity. An EFA in the first study used a maximum likelihood estimation method with a principal factor analysis. The second study narrowed the descriptors and evaluated the factor structure with a confirmatory factor analysis (CFA). Results:, Two factors were retained in the solution; one contained five items with descriptors of physical symptoms, and a second contained five items with psychological symptoms. CFA determined that the two five-item scales were stable and reliable measures of patient nausea experience. Conclusions:, The scales measure both physical and psychological symptoms of nausea, indicating that the experience is multidimensional. ACADEMIC EMERGENCY MEDICINE 2010; 17:e33,e39 © 2010 by the Society for Academic Emergency Medicine [source] Self-efficacy for coping with cancer: revision of the Cancer Behavior Inventory (version 2.0)PSYCHO-ONCOLOGY, Issue 3 2001Thomas V. Merluzzi The Cancer Behavior Inventory (CBI), a measure of self-efficacy for coping with cancer, was revised by adding a new stress management scale and reducing its length from 43 to 33 items. The 33-item CBI was administered to 280 cancer patients. A principal factors analysis with varimax rotation yielded the hypothesized seven factors (,s in parentheses): (1) maintenance of activity and independence (,=0.86), (2) seeking and understanding medical information (,=0.88), (3) stress management (,=0.86), (4) coping with treatment-related side-effects (,=0.82), (5) accepting cancer/maintaining positive attitude (,=0.86), (6) affective regulation (,=0.81), and (7) seeking support (,=0.80). The , for the entire CBI was 0.94, the test-retest (1 week) reliability coefficient was 0.74, and correlations with measures of quality of life and coping supported its validity. The CBI may be useful to researchers and clinicians and can be integrated into a self-regulation model of coping. Copyright © 2001 John Wiley & Sons, Ltd. [source] | |||||||||||||