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Common Variance (common + variance)
Selected AbstractsMultilevel models for estimating incremental net benefits in multinational studiesHEALTH ECONOMICS, Issue 8 2007Richard Grieve Abstract Multilevel models (MLMs) have been recommended for estimating incremental net benefits (INBs) in multicentre cost-effectiveness analysis (CEA). However, these models have assumed that the INBs are exchangeable and that there is a common variance across all centres. This paper examines the plausibility of these assumptions by comparing various MLMs for estimating the mean INB in a multinational CEA. The results showed that the MLMs that assumed the INBs were exchangeable and had a common variance led to incorrect inferences. The MLMs that included covariates to allow for systematic differences across the centres, and estimated different variances in each centre, made more plausible assumptions, fitted the data better and led to more appropriate inferences. We conclude that the validity of assumptions underlying MLMs used in CEA need to be critically evaluated before reliable conclusions can be drawn. Copyright © 2006 John Wiley & Sons, Ltd. [source] Measuring consumer perception of product creativity: Impact on satisfaction and purchasabilityHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 3 2009Diana Horn In the current value-based economy, product creativity is a potential resource for organizations to compete, thus emphasizing the need for product creativity measurement. Two studies were performed to refine and validate a previously tested model and measurement of consumer perception of product creativity: one with web-based evaluations (N = 208) of chairs and lamps and one with paper-based evaluations (N = 105) of individually selected products. Results of exploratory factor analyses indicated three main product creativity factors: Affect, Importance, and Novelty, which explained 72% of the common variance. Results of stepwise regressions indicated that the Affect factor significantly predicts (65% of the explained variance) willingness to purchase creative consumer products. One major contribution of this research is the finding that affect is as equally (R2 = .28) important as novelty (R2 = .25) in consumer perception of product creativity. Theoretical and practical implications are discussed for the Affect, Importance, and Novelty product creativity factors, and general creativity guidelines are provided for consumer product design. © 2009 Wiley Periodicals, Inc. [source] Validation of the Learning Transfer System Inventory: A study of supervisors in the public sector in JordanHUMAN RESOURCE DEVELOPMENT QUARTERLY, Issue 3 2008Abdulfattah Yaghi Jordanian policymakers rely on trained supervisors to lead organizational change in public administration. The impact of training, however, remains weak unless trainees apply what they have learned (training transfer). In order to assess training transfer, the present study validates a Classic Arabic version of the Learning Transfer System Inventory (CALTSI). The instrument was administered to a random sample of 500 supervisors. Exploratory factor analysis with oblique factor rotation validates 15 of the original 16 factors of the LTSI and explains about 65% of the common variance. These findings and their implications are discussed. [source] Perspectives on Models of Job PerformanceINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 4 2000Chockalingam Viswesvaran Contemporary models of job performance are reviewed. Links between task performance, contextual performance, organizational citizenship behaviors, counterproductivity and organizational deviance are pointed out. Measurement issues in constructing generic models applicable across jobs are discussed. Implications for human resource management in general, and performance appraisal for selection and assessment in particular, are explored. It is pointed out that the different dimensions or facets of individual job performance hypothesized in the literature are positively correlated. This positive manifold suggests the presence of a general factor which represents a common variance shared across all the dimensions or facets. Although no consensus exists in the extant literature on the meaning and source of this shared variance (i.e., the general factor), rater idiosyncratic halo alone does not explain this general factor. Future research should explain the common individual differences determinants of performance dimensions. [source] Generalized least-squares parameter estimation from multiequation implicit modelsAICHE JOURNAL, Issue 10 2003Simon L. Marshall Maximum likelihood fit of nonlinear, implicit, multiple-response models to data containing normally distributed random errors can be carried out by a combination of the Gauss-Newton generalized nonlinear least-square algorithm first described by Britt and Luecke in 1973, with a Fletcher-Reeves conjugate gradient search for initial parameter estimates. The convergence of the algorithm is further improved by adding a step-limiting procedure that ensures a reduction in the objective function for each iteration. Multiple-equation regression methods appropriate to the solution of explicit fixed-regressor models are derived from this general treatment as special cases. These include weighted nonlinear least squares (where the covariance matrix of the response is known), and uniformly weighted nonlinear least squares (where the responses are uncorrelated and characterized by a single common variance). Alternative methods for fixed-regressor fits of explicit multiequation models with an unknown covariance matrix of the responses are also considered. The moment-matrix determinant criterion appropriate in such situations is also efficiently minimized by use of the conjugate-gradient algorithm, which is considerably less sensitive to the accuracy of the initial parameter estimate than the more usual Gauss-Newton methods. The performance of the new algorithm for models defined by one, two, and three implicit functional constraints per point is illustrated by random-regressor fits of isothermal p,X and p,X,Y vapor,liquid equilibrium data, and ternary liquid,liquid equilibrium data, respectively. [source] Second Language Listening: Listening Ability or Language Proficiency?MODERN LANGUAGE JOURNAL, Issue 1 2006LARRY VANDERGRIFT This article reports on a study exploring the respective contributions of first language (L1) listening comprehension ability and second language (L2) proficiency to L2 listening comprehension ability. The participants were 75 Grade 8 English-speaking students learning French. The students completed tests in French and in English that required them to listen to authentic dialogues and to complete a number of multiple choice comprehension questions. Multiple regression analysis indicated that both L1 listening comprehension ability and L2 proficiency contributed significantly to L2 listening comprehension ability, with L2 proficiency having about twice as much common variance. A further analysis by question type indicated that, although the relative contribution of L2 proficiency to the combined variance continued to be higher for both question types, the relative contribution of L1 listening comprehension ability to answering literal questions was greater than for answering inferencing questions. The results are discussed in light of the linguistic threshold and the linguistic interdependence hypotheses and similar research on this same question for L2 reading. This article initiates an exploration of the ability/proficiency debate as it relates to L2 listening comprehension ability, discusses implications for L2 pedagogy, and suggests important avenues for further research. [source] Psychometric characteristics of dyspnea descriptor ratings in emergency department patients with exacerbated chronic obstructive pulmonary disease,RESEARCH IN NURSING & HEALTH, Issue 5 2002Mark B. Parshall Abstract The purpose of this study was to evaluate the reliability, content validity, and factor structure of dyspnea sensory quality descriptor ratings in emergency department (ED) patients with exacerbated chronic obstructive pulmonary disease (COPD). During an ED visit 104 patients with COPD rated the intensity of 16 dyspnea sensory quality descriptors (numerical ratings of 0,10) in relation to how they felt when they decided to come to the ED (Decision) and 1 week before the visit. Content validity of 15 descriptors was supported. Factor analysis of Decision ratings resulted in seven descriptors and three factors (,=.88; 74% common variance): Smothering/Suffocating/Hunger for air (,=.87); Effort/Work (,=.87); and Tight/Constricted (,=.74). Results indicate that the intensity of sensory quality descriptors can be measured reliably in COPD patients during an exacerbation of COPD. The initial descriptor list of descriptors could be cut by more than half while retaining satisfactory psychometric properties. © 2002 Wiley Periodicals, Inc. Res Nurs Health 25:331,344, 2002 [source] An Age-Stratified Poisson Model for Comparing Trends in Cancer Rates Across Overlapping RegionsBIOMETRICAL JOURNAL, Issue 4 2008Yi Li Abstract The annual percent change (APC) has been used as a measure to describe the trend in the age-adjusted cancer incidence or mortality rate over relatively short time intervals. The yearly data on these age-adjusted rates are available from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute. The traditional methods to estimate the APC is to fit a linear regression of logarithm of age-adjusted rates on time using the least squares method or the weighted least squares method, and use the estimate of the slope parameter to define the APC as the percent change in the rates between two consecutive years. For comparing the APC for two regions, one uses a t-test which assumes that the two datasets on the logarithm of the age-adjusted rates are independent and normally distributed with a common variance. Two modifications of this test, when there is an overlap between the two regions or between the time intervals for the two datasets have been recently developed. The first modification relaxes the assumption of the independence of the two datasets but still assumes the common variance. The second modification relaxes the assumption of the common variance also, but assumes that the variances of the age-adjusted rates are obtained using Poisson distributions for the mortality or incidence counts. In this paper, a unified approach to the problem of estimating the APC is undertaken by modeling the counts to follow an age-stratified Poisson regression model, and by deriving a corrected Z -test for testing the equality of two APCs. A simulation study is carried out to assess the performance of the test and an application of the test to compare the trends, for a selected number of cancer sites, for two overlapping regions and with varied degree of overlapping time intervals is presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The Family Dermatology Life Quality Index: measuring the secondary impact of skin diseaseBRITISH JOURNAL OF DERMATOLOGY, Issue 3 2007M.K.A. Basra Summary, Background, Skin diseases are known to have a major impact on the lives of patients and their families. Many instruments are available to measure the health-related quality of life (HRQoL) of patients but no measure has been developed so far to quantify the secondary impact on family members of the patients. Objectives, To develop and validate a dermatology-specific instrument to measure the adverse impact on the HRQoL of family members of patients with skin disease. Methods, Detailed semi-structured interviews were conducted with family members of patients to identify different aspects of HRQoL affected. An initial draft version of the questionnaire based on the main topic areas was pilot tested to assess the face and content validity. A 10-item questionnaire, the Family Dermatology Life Quality Index (FDLQI), was finalized after modifications to the draft questionnaire based on feedback from families and dermatology professionals and on item reduction. Psychometric evaluation was conducted on a new cohort of family members (n = 132) who completed the FDLQI and the patients (n = 109) who completed the Dermatology Life Quality Index (DLQI). Results, Fifty-nine different aspects of family members' HRQoL were identified from the analysis of the interviews, which were categorized into main topic areas. Factor analysis of 10 items of the final questionnaire revealed two factors and together these explained 60% of the common variance. The FDLQI demonstrated high internal consistency (Cronbach's , = 0·88) and test,retest (intraclass correlation coefficient = 0·94) reliabilities. The responsiveness of the instrument to change was shown by significant change in the family members' FDLQI scores in cases where patients' clinical condition either improved or worsened. Construct validity was assessed by testing a number of a priori hypotheses. A strong correlation was seen between the family members' FDLQI scores and patients' DLQI scores (r = 0·69), a significantly higher FDLQI score was seen for inflammatory skin diseases compared with noninflammatory diseases/isolated lesions (P < 0·0001), and there was a positive relationship between the family members' FDLQI scores and patients' disease severity (r = 0·49). Conclusions, The FDLQI is simple and practical and seems to have the potential to be used as an additional outcome measure in clinical practice and evaluation research. [source] | |||||||||||||