Single Common Factor Research Articles

Using the Results of Qualitative Surveys in Quantitative Analysis

The answers to qualitative questions put to economic operators can be integrated in standard macro-economic analysis by using a procedure chosen among the probabilistic approach, the regression methods or the factor approach. The first one is the most commonly used. It is based on the assumption that the respondents reply that the value of the reference variable x can be described by a certain statement (e.g.: x stays stable) if it lies between two known thresholds (e.g.: ±5% around its initial value). A number of quantified indicators may be derived by assuming a special functional form for the frequency distribution of opinions and expectations of respondents about x. According to the regression approach, the respondents attach to each qualitative answer a reference value of x, which can be estimated by regressing an available quantitative measure of x against the time series (or longitudinal samples) of percentages of people who gave each qualitative answer. Finally, one can assume that every percentage of answers is driven by a single common latent factor, which can be estimated by applying to the percentages of answers the standard tools of multivariate statistics. All of the three approaches include as a special case the balance statistic, adopted very often in empirical analyses. Both the theoretical analysis and the empirical evidence on the relative merits of various methods are mixed. In general, no single quantification technique clearly outperforms the others, at least in preliminary analysis. However, when the quantified indicators must be included as explanatory variables in standard econometric models, the regression approach seems the most suitable and natural one. On its turn, the factor approach provides a profitable alternative to the regression method in exploratory analyses and when multicollinearity and degrees of freedom of estimates become severe constraints.

Search for a Common Cause Factor amongst Cognitive, Speed and Biological Variables Using Narrow Age Cohorts

Background: Cross-sectional studies have demonstrated that age-related effects on many cognitive and biological functioning variables are shared. A number of theories postulate that these associations arise from a common causal mechanism responsible for change across a wide range of functions. However, it has been claimed that the finding of shared variance among variables in these studies may be spurious because most studies have been cross-sectional and based on age-heterogeneous samples. Objective: To examine evidence for changes with age in variance shared by cognitive variables using a narrow-age cohort design. Methods: Three samples of adults with age ranges 20–24 years (n = 2,404), 40–44 years (n = 2,530) and 60–64 years (n = 2,510) were drawn from a population-based study. These groups were supplemented by data from an older sample of individuals (77 years and over) from a second population-based study (n = 374). Four models of the structure of a range of cognitive, speed and biological variables derived from previous cross-sectional research were fitted to data. These models were complete independence of variables within a cohort, a single common factor, multiple independent factors, and a second order factor model. Results: Model fit and the magnitude of loadings from multiple-group confirmatory factor analyses was compared between age groups. The fit for all four models was worse in the 60–64 year age group. Factor loadings on the common factor specified in these models varied between the groups, but the speed factor rather than the biological factor showed increased loadings as a function of age. Conclusions: This narrow age-cohort study did not support the existence of developmental changes in the structure of cognitive and biological variables across the lifespan. Shared variation between measures of cognition and biological function may be an artifact of the research designs that have generated these findings. This casts doubt of the existence of a common causal mechanism. However, it may be that such changes manifest only in later old age.

Consilience and Life History Theory: From genes to brain to reproductive strategy

We describe an integrated theory of individual differences that traces the behavioral development of life history from genes to brain to reproductive strategy. We provide evidence that a single common factor, the K-Factor, underpins a variety of life-history parameters, including an assortment of sexual, reproductive, parental, familial, and social behaviors. We explore the psychometrics and behavioral genetics of the K-Factor and offer a speculative account of the proximate mediation of this adaptive patterning of behavior as instantiated in well-established functions of specific areas of the human brain, including the frontal lobes, amygdala, and hippocampus. We then apply Life History Theory to predict patterns of development within the brain that are paedomorphic (i.e., development begins later, proceeds at a slower rate, and has an earlier cessation) and peramorphic (i.e., development begins early, proceeds at a faster rate, and has a later cessation).

Rating Scale, Standard Gamble, and Time Trade-off for People With Traumatic Spinal Cord Injuries

The rating scale (RS), standard gamble (SG), and time trade-off (TTO) for people with traumatic spinal cord injuries (SCIs) have not been reported. This study compared psychometric performances of these preference-based measures among people with SCIs in Taiwan. In total, 187 subjects from a nationwide registry of people with traumatic SCIs were interviewed by telephone. Score distributions, interrater reliability, discriminant ability, and convergent validity for the RS, SG, and TTO were compared. The mean (median) values of the RS, SG, and TTO were 0.67 (0.70), 0.64 (0.75), and 0.53 (0.50), respectively, and their corresponding intraclass correlation coefficients for intrarater and interrater test-retest reliability were .92 and .89, .78 and .73, and .91 and .78. Compared with the SG and TTO, the RS had fewer floor and ceiling values as well as percent changes, more missing observations, a larger effect size, and better discrimination ability. The results of Spearman correlation and factor analysis showed that the SG strongly converged with the TTO (r=.65, and in a single common factor), but they weakly converged with the RS (r=.33 with the SG and r=.27 with the TTO). In the linear regression models, the RS was significantly associated with neurological severity, employment, educational level, and self-care ability; the SG was associated with neurological severity and employment; and the TTO was associated only with neurological severity. The RS generally performed better than the SG and TTO among people with traumatic SCIs; however, the underlying construct measured by the RS differed considerably from those measured by the SG and TTO.

Do We Need to Worry about Credit Risk Correlation?

Yes we do. This article shows that any firm9s credit risk is, to a very large extent, driven by common risk factors affecting all firms. Using a reduced form model and sequential Kalman filtering estimation, we decompose the credit risk of a sample of corporate bonds (14 U.S. firms, 2001–2003) into different unobservable risk factors. A single common factor accounts for more than 50% of all (but two) of the firms9 credit risk levels, with an average of 68% across firms. This factor represents the credit risk levels underlying the U.S. economy and is strongly correlated with main U.S. stock indexes.

A Single Factor Underlies the Metabolic Syndrome

OBJECTIVE—Confirmatory factor analysis (CFA) was used to test the hypothesis that the components of the metabolic syndrome are manifestations of a single common factor. RESEARCH DESIGN AND METHODS—Three different datasets were used to test and validate the model. The Spanish and Mauritian studies included 207 men and 203 women and 1,411 men and 1,650 women, respectively. A third analytical dataset including 847 men was obtained from a previously published CFA of a U.S. population. The one-factor model included the metabolic syndrome core components (central obesity, insulin resistance, blood pressure, and lipid measurements). We also tested an expanded one-factor model that included uric acid and leptin levels. Finally, we used CFA to compare the goodness of fit of one-factor models with the fit of two previously published four-factor models. RESULTS—The simplest one-factor model showed the best goodness-of-fit indexes (comparative fit index 1, root mean-square error of approximation 0.00). Comparisons of one-factor with four-factor models in the three datasets favored the one-factor model structure. The selection of variables to represent the different metabolic syndrome components and model specification explained why previous exploratory and confirmatory factor analysis, respectively, failed to identify a single factor for the metabolic syndrome. CONCLUSIONS—These analyses support the current clinical definition of the metabolic syndrome, as well as the existence of a single factor that links all of the core components.

Multivariate Genetic Analysis of Academic Skills of the Queensland Core Skills Test and IQ Highlight the Importance of Genetic <I>g</I>

This study examined the genetic and environmental relationships among 5 academic achievement skills of a standardized test of academic achievement, the Queensland Core Skills Test (QCST; Queensland Studies Authority, 2003a). QCST participants included 182 monozygotic pairs and 208 dizygotic pairs (mean 17 years +/- 0.4 standard deviation). IQ data were included in the analysis to correct for ascertainment bias. A genetic general factor explained virtually all genetic variance in the component academic skills scores, and accounted for 32% to 73% of their phenotypic variances. It also explained 56% and 42% of variation in Verbal IQ and Performance IQ respectively, suggesting that this factor is genetic g. Modest specific genetic effects were evident for achievement in mathematical problem solving and written expression. A single common factor adequately explained common environmental effects, which were also modest, and possibly due to assortative mating. The results suggest that general academic ability, derived from genetic influences and to a lesser extent common environmental influences, is the primary source of variation in component skills of the QCST.

Multivariate Genetic Analysis of Academic Skills of the Queensland Core Skills Test and IQ Highlight the Importance of Geneticg

AbstractThis study examined the genetic and environmental relationships among 5 academic achievement skills of a standardized test of academic achievement, the Queensland Core Skills Test (QCST; Queensland Studies Authority, 2003a). QCST participants included 182 monozygotic pairs and 208 dizygotic pairs (mean 17 years ± 0.4 standard deviation). IQ data were included in the analysis to correct for ascertainment bias. A genetic general factor explained virtually all genetic variance in the component academic skills scores, and accounted for 32% to 73% of their phenotypic variances. It also explained 56% and 42% of variation in Verbal IQ and Performance IQ respectively, suggesting that this factor is genetic g. Modest specific genetic effects were evident for achievement in mathematical problem solving and written expression. A single common factor adequately explained common environmental effects, which were also modest, and possibly due to assortative mating. The results suggest that general academic ability, derived from genetic influences and to a lesser extent common environmental influences, is the primary source of variation in component skills of the QCST.

The K-factor: Individual differences in life history strategy

Until recently, variations in life history strategy were studied exclusively at the species level. Although this domain of study has been extended to examine systematic differences in life history strategy among various human ethnic groupings, more recent evolutionary theories of human development and related behavioral genetic work imply substantial within-group individual variation in life history strategy. We constructed a latent variable model identifying a single common factor, denoted as K, which underlies a variety of otherwise disparate life history parameters. This “ K-Factor” loaded 0.36 on childhood attachment to the biological father, −0.36 on childhood attachment to any non-biological father figure, 0.38 on adult romantic partner attachment, −0.51 on mating effort, −0.58 on Machiavellianism, and −0.41 on risk propensity. The bivariate correlations of the K-factor with higher-order personality factors were statistically significant, −0.24 with “Big Neuroticism” and −0.67 with “Big Psychoticism”, and approached significance, correlating 0.12, with “Big Extraversion”. The K-factor appears to be an underappreciated individual difference variable of major importance to human development.

Contributions of Genes and Environments to Stability and Change in Externalizing and Internalizing Problems During Elementary and Middle School

We examined longitudinally collected behavioral reports by teachers on a unique twin sample at the ages of 7, 8, 9, 10, 11, and 12 years. As twin and adoption studies implicate the role of genetic influence on behavioral problems found to be stable in epidemiological samples, the current study employs a developmental behavior genetic model to examine the extent to which genetic and environmental contributions to problem behaviors are stable and/or change during development. In this sample of 410 monozygotic (MZ) and 354 dizygotic (DZ) twins, MZ twins were rated as more similar than DZ twins on average. In general, boys were more frequently rated as displaying externalizing behaviors than were girls across each of the six observations, while girls' internalizing problems were found not to be significantly different from boys'. For both sexes, stability in externalizing problem behaviors was due to a single common genetic factor whose effects acted pleiotropically at each age in the presence of unique environmental influences that were transmitted from age-to-age. Change was largely due to uncorrelated age-specific non-shared environmental and additive genetic effects. Contributions to stability for internalizing problems were due to age-to-age transmission of earlier expressed genetic effects. Change for girls and boys internalizing problems were largely due to environmental experiences unique to siblings along with uncorrelated age-specific genetic effects. These results further inform the notion that individual environments are important factors in the etiology of problem behaviors, but suggest that heritable contributions to phenotypic stability are largely the same across middle childhood and early adolescence. Clinical implications of these findings are discussed.

Capital Allocation for Portfolio Credit Risk

Capital allocation rules are derived that maximize leverage while maintaining a target solvency rate for credit portfolios where risk is driven by a single common factor and idiosyncratic risk is fully diversified. Equilibrium conditions ensure that capital allocations depend on interest earnings as well as credits' probability of default, endogenous loss given default, and asset correlation. Capitalization rates exceed those estimated using Gaussian credit loss models. Results demonstrate that credit risk is undercapitalized by the Basel II AIRB approach in part because of ambiguities regarding the definition of loss given default. An alternative proposed capital rule removes this bias.

Sudden Unexpected Death in Epilepsy

Patients with epilepsy have a mortality rate higher than that of the general population; sudden unexpected death represents a significant category of mortality in these patients. The precise frequency of occurrence of sudden unexpected death in epilepsy (SUDEP) is not well defined, with a range of 1 in 370 to 1100 in the general epileptic population. A major difficulty with incidence studies is the continued reluctance in using the term SUDEP as a cause of death, making reliance solely on death certificates inconsistent and incomplete. Knowledge about SUDEP remains limited, as no single common risk factor has yet been identified, although predisposing conditions have been suggested. The purpose of this study is to review the association between several clinical variables and SUDEP to elucidate risk factors. The characteristics of the 67 cases in this series correlate with published findings in previous studies. Attributes that may be used to define an at-risk group of epileptics include age less than 40 years, male gender, long history of seizure disorder, undermedication or poorly controlled seizure activity, and mental or physical stress. Education of physicians as to the existence of SUDEP and risk factors is imperative in improving patient education and reduction in mortality.

The Structure of Genetic and Environmental Risk Factors for Anxiety Disorders in Men and Women

The anxiety disorders exhibit high levels of lifetime comorbidity with one another. Understanding the underlying causes of this comorbidity can provide insight into the etiology of the disorders and inform classification and treatment. To explain anxiety disorder comorbidity by examining the structure of the underlying genetic and environmental risk factors. Lifetime diagnoses for 6 anxiety disorders (generalized anxiety disorder, panic disorder, agoraphobia, social phobia, animal phobia, and situational phobia) were obtained during personal interviews from a population-based twin registry. Multivariate structural equation modeling that allowed for sex differences was performed. General community sample. More than 5000 members of male-male and female-female twin pairs from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders. Parameter estimates for best-fitting model. The full model, which contained 2 common genetic, shared environmental, and unique environmental factors plus disorder-specific factors, could be constrained to equality across male and female study participants. In the best-fitting model, the genetic influences on anxiety were best explained by 2 additive genetic factors common across the disorders. The first loaded most strongly in generalized anxiety disorder, panic disorder, and agoraphobia, whereas the second loaded primarily in the 2 specific phobias. Social phobia was intermediate in that it was influenced by both genetic factors. A small role for shared environmental influences was observed owing to a single common factor that accounted for less than 12% of the total variance for any disorder. Unique environmental influences could be explained by a single common factor plus disorder-specific effects. The underlying structure of the genetic and environmental risk factors for the anxiety disorders is similar between men and women. Genes predispose to 2 broad groups of disorders dichotomized as panic-generalized-agoraphobic anxiety vs the specific phobias. The remaining associations between the disorders are largely explained by a unique environmental factor shared across the disorders and, to a lesser extent, a common shared environmental factor.

Do We Need to Worry about Credit Risk Correlation?

Yes we do. This paper shows that any firm's credit risk is, to a very large extent, driven by common risk factors affecting all firms. Using a reduced form model and sequential Kalman filtering estimation we decompose the credit risk of a sample of corporate bonds (14 US firms, 2001-2003) into different unobservable risk factors. A single common factor accounts for more than 50% of all (but two) of the firms' credit risk levels, with an average of 68% across firms. Such factor represents the credit risk levels underlying the US economy and is strongly correlated with main US stock indexes.

Unbiased Capital Allocation in an Asymptotic Single Risk Factor (ASRF) Model of Credit Risk

This paper derives unbiased capital allocation rules for portfolios in which credit risk is driven by a single common factor and idiosyncratic risk is fully diversified. The methodology for setting unbiased capital allocations is developed in the context of the Black-ScholesMerton (BSM) equilibrium model. The methodology is extended to develop an unbiased capital allocation rule for the Gaussian ASRF structural model of credit risk. Unbiased capital allocations are shown to depend on yield to maturity as well as probability of default, loss given default, and asset correlations. Unbiased capital allocations are compared to capital allocations that are set equal to unexpected loss in a Gaussian credit loss model—an approach that is widely applied in the banking industry and used to set minimum bank regulatory capital standards under the Basel II Internal Ratings Based (IRB) approach. The analysis demonstrates that the Gaussian unexpected loss approach substantially undercapitalizes portfolio credit risk relative to an unbiased capital allocation rule. The results include a suggested correction for the IRB capital assignment function. The corrected capital rule calls for a substantial increase in minimum capital requirements over the existing Basel II IRB regulatory capital function.

A common genetic factor underlies hypertension and other cardiovascular disorders

BackgroundCertain conditions characterised by blood vessel occlusion or vascular spasm have been found to cluster together in epidemiological studies. However the biological causes for these associations remain controversial. This study used a classical twin design to examine whether these conditions are linked through shared environmental exposures or by a common underlying genetic propensity to vasospasm.MethodsWe investigated the association between hypertension, migraine, Raynaud's phenomenon and coronary artery disease in twins from a national register. Phenotype status was determined using a questionnaire and the genetic and environmental association between phenotypes was estimated through variance components analysis.ResultsResponses were obtained from 2,204 individuals comprising 525 monozygotic and 577 dizygotic pairs. There was a significant genetic contribution to all four traits with heritabilities ranging from 0.34 to 0.64. Multivariate model-fitting demonstrated that a single common genetic factor underlies the four conditions.ConclusionsWe have confirmed an association between hypertension, migraine, Raynaud's phenomenon and coronary artery disease, and shown that a single genetic factor underlies them. The demonstration of a shared genetic factor explains the association between them and adds weight to the theory of an inherited predisposition to vasospasm.

Cash Flows and Discount Rates, Industry and Country Effects, and Co-Movement in Stock Returns

This paper examines the relative importance of global, country-specific, and industry-specific factors in both the cash flow and discount rate components of equity returns between 1995 and 2003. Our framework draws upon previously separate literatures on country versus industry effects and (forward-looking) cash flow versus discount rate components of equity return innovations. We apply the Campbell (1991) decomposition for industry-by-country, all-country, global industry, and world market index returns so we can produce a richer characterization of same-industry and same-country effects in stock returns. Unlike previous equity return decomposition papers, we exploit information in equity analysts' earnings forecasts when projecting future variables from our reduced-form equation systems. Our findings confirm previous research that finds patterns of correlation that suggest a richer underlying structure than just a single common global factor. Furthermore, our results suggest that global, within-country, and same-industry effects are all important for both of the two key components of stock returns: news about future dividends and news about future discount rates. In particular, within-industry covariation in news about future discount rates appears to be just as important as within-country covariation in news about future discount rates. We also find that the idiosyncratic component of cash flow news is more important than the global component, while the reverse is true for news about future discount rates. Our results are broadly consistent with co-movement in future discount rates arising from perceptions of common elements of risk, rather than national market segmentation.

Genome-wide linkage analysis of a composite index of neuroticism and mood-related scales in extreme selected sibships.

There is considerable evidence to suggest that the genetic vulnerabilities to depression and anxiety substantially overlap and quantitatively act to alter risk to both disorders. Continuous scales can be used to index this shared liability and are a complementary approach to the use of clinical phenotypes in the genetic analysis of depression and anxiety. The aim of this study (Genetic and Environmental Nature of Emotional States in Siblings) was to identify genetic variants for the liability to depression and anxiety after the application of quantitative genetic methodology to a large community-based sample (n = 34,371), using four well-validated questionnaires of depression and anxiety. Genetic model fitting was performed on 2658 unselected sibships, which provided evidence for a single common familial factor that accounted for a substantial proportion of the genetic variances and covariances of the four scales. Using the parameter estimates from this model, a composite index of liability (G) was constructed. This index was then used to select a smaller--but statistically powerful--sample for DNA collection (757 individuals, 297 sibships). These individuals were genotyped with more than 400 microsatellite markers. After the data were checked and cleaned, linkage analysis was performed on G and the personality scale of neuroticism using the regression-based linkage program MERLIN-REGRESS. The results indicated two potential quantitative trait loci (QTL): one on chromosome 1p (LOD 2.2) around 64 cM (43-70 cM) near marker D1S2892 and another on chromosome 6p (LOD 2.7) around 47 cM (34-63 cM) near marker D6S1610. Further exploratory sex-specific analyses suggested that these QTLs might have sex-limited effects.

Acute pain services in the United Kingdom

Abstract This survey addresses the structure and function of the acute pain services (APS) in the UK 10 years after its initial commencement. APS is now available in many hospitals (89.4%). The APS team consists mainly of anaesthetists, occasionally includes nurses and pharmacists, and rarely physiotherapists and psychologists. Anaesthetists, mainly, cover the out-of-hours service and nurses only occasionally. Dedicated medical staff sessions did not exist in 37%, and were limited to 1–2 sessions per week in 49% of the hospitals that responded to the questionnaire. Regular training commitment by medical staff did not exist in 25% of hospitals. Frequency of nursing training sessions varied from nil in 12% to almost monthly in 40% of hospitals. Patient controlled analgesia (PCA) and epidurals were available for post-operative analgesia in almost every single hospital responding to this questionnaire. Protocols for epidurals were available in 92% of hospitals, without clear relationship to the actual presence of APS. Anaesthetists designed these protocols in 27%, nurses in 1%, both anaesthetists and nurses in 43% and the whole team in 20% of hospitals. Written consent for epidurals was rarely obtained. The place of care for patients with post-operative epidural analgesia was surgical wards in 73%, HDU in 51% and ITU in 48% of respondent hospitals. The most single common factor in the decision on place of care was the availability of trained nursing staff. Monitoring usually comprised respiratory rate, sedation and pulse oximetry. Bupivacaine 0.1% was the most commonly used local anaesthetic for post-operative epidural analgesia, while diamorphine followed by fentanyl were the most commonly used epidural opioids. Other adjuvants to epidurals were rarely ever used; only clonidine was used in 7% of hospitals. Continuous epidural infusions were used in 84% of hospitals while patient controlled epidural analgesia PCEA was used only in 19% of hospitals.

General and specific cognitive deficits in schizophrenia

BackgroundIt is controversial whether the cognitive deficit in schizophrenia is better characterized as generalized or as reflecting relatively independent deficits in different cognitive domains. The issue has implications for assessment practice, intervention design, and the exploration of schizophrenia genetics. MethodsWe used a specialized structural equation modeling approach, single common factor analysis, to explore the relative importance of generalized versus independent cognitive deficits in schizophrenia. Eighteen subtest scores from the Wechsler Adult Intelligence Scale-III and the Wechsler Memory Scale-III were included in the analysis. We analyzed these data for 97 schizophrenia or schizoaffective disorder outpatients and 87 healthy control subjects. ResultsApproximately two thirds of the overall effect of a schizophrenia diagnosis on cognitive performance was mediated through a single common factor. The Wechsler subtest scores showed almost uniformly strong relationships with this factor. The independent associations of group status with the subtest scores were smaller in magnitude and only selectively significant. ConclusionsThe relatively greater magnitude of illness effects mediated through the common factor in this analysis, compared with the specific, independent effects, suggests that a generalized cognitive deficit is a core feature of schizophrenia.