Overfactoring in rating scale data: A comparison between factor analysis and item response theory

Educational and psychological measurement is typically based on dichotomous variables or rating scales comprising a few ordered categories. When the mean of the observed responses approaches the upper or the lower bound of the scale, the distribution of the data becomes skewed and, if a categorical factor model holds in the population, the Pearson correlation between variables is attenuated. The consequence of this correlation attenuation is that the traditional linear factor model renders an excessive number of factors. This article presents the results of a simulation study investigating the problem of overfactoring and some solutions. We compare five widely known approaches: (1) The maximum-likelihood factor analysis (FA) model for normal data, (2) the categorical factor analysis (FAC) model based on polychoric correlations and maximum likelihood (ML) estimation, (3) the FAC model estimated using a weighted least squares algorithm, (4) the mean corrected chi-square statistic by Satorra-Bentler to handle the lack of normality, and (5) the Samejima's graded response model (GRM) from item response theory (IRT). Likelihood-ratio chi-square, parallel analysis (PA), and categorical parallel analysis (CPA) are used as goodness-of-fit criteria to estimate the number of factors in the simulation study. Our results indicate that the maximum-likelihood estimation led to overfactoring in the presence of skewed variables both for the linear and categorical factor model. The Satorra-Bentler and GRM constitute the most reliable alternatives to estimate the number of factors.

What are the consequences of ignoring cross-loadings in bifactor models? A simulation study assessing parameter recovery and sensitivity of goodness-of-fit indices

Bifactor latent models have gained popularity and are widely used to model construct multidimensionality. When adopting a confirmatory approach, a common practice is to assume that all cross-loadings take zero values. This article presents the results of a simulation study exploring the impact of ignoring non-zero cross-loadings on the performance of confirmatory bifactor analysis. The present work contributes to previous research by including study conditions that had not been examined before. For instance, a wider range of values of the factor loadings both for the group factors and the cross-loadings is considered. Parameter recovery is analyzed, but the focus of the study is on assessing the sensitivity of goodness-of-fit indices to detect the model misspecification that involves ignoring non-zero cross-loadings. Several commonly used SEM fit indices are examined: both biased estimators of the fit index (CFI, GFI, and SRMR) and unbiased estimators (RMSEA and SRMR). Results indicated that parameter recovery worsens when ignoring moderate and large cross-loading values and using small sample sizes, and that commonly used SEM fit indices are not useful to detect such model misspecifications. We recommend the use of the unbiased SRMR index with a cutoff value adjusted by the communality level (R²), as it is the only fit index sensitive to the model misspecification due to ignoring non-zero cross-loadings in the bifactor model. The results of the present study provide insights into modeling cross-loadings in confirmatory bifactor models but also practical recommendations to researchers.

Nominal Factor Analysis of Situational Judgment Tests: Evaluation of Latent Dimensionality and Factorial Invariance

Situational judgment tests have gained popularity in educational and psychological measurement and are widely used in personnel assessment. A situational judgment item presents a hypothetical scenario and a list of actions, and the individuals are asked to select their most likely action for that scenario. Because actions have no explicit order, the item generates nominal responses consisting of the actions selected by the individuals. This article shows how to factor-analyze the nominal responses originated from such a test, including the estimation of the number of latent factors and a factor invariance analysis in a multiple group design. The method consists of applying the MNCM, a multidimensional extension of the nominal categories model by Bock. The article includes the results of two studies: (1) a simulation study about Type-I error rate, statistical power, and recovery of the parameters in a multigroup factorial invariance design and (2) a real data example using responses to a situational judgment test measuring gender stereotypes to illustrate the approach. Results suggest the use of the Akaike information criterion, Bayesian information criterion, and corrected Bayesian information criterion indices to guide the selection of the number of factors with nominal responses. All the analyses are conducted using the computer program Mplus. The code is included as Supplemental Material (available online) for the readers so that they can adapt it to their own purposes.

Validation of a Questionnaire for Personality Profiling using Cognitive Diagnostic Modeling

This article describes the development of the ENCUIST (Extroversion, Neuroticism, Callous-Unemotional, Instability, Short-Test) questionnaire, which has been created to provide a personality profiling method based on a cognitive diagnostic modeling framework. The ENCUIST measures the attributes of extroversion, neuroticism, callous unemotionality and overt expressions of anger that are relevant in a forensic context. The scores provided by the ENCUIST are binary classifications of the individuals (high/low) in these attributes. The ENCUIST was developed using a sample of 516 subjects to study its validation through psychometric procedures, including factor analysis, cognitive diagnostic modeling and structural equation modeling. The results supported a four-factor structure. Linear regressions were used to evaluate the predictive validity of the scores provided by ENCUIST with respect to two external criteria that are relevant in the forensic context, namely behavioral activation and behavioral inhibition. The results showed that the extroversion dimension is positively related to behavioral activation, although the effect size is modest and the proportion of explained variance is only 11%. Moreover, the dimensions of neuroticism and anger expression are positively related to behavioral inhibition, with 7% of the variance explained. Together, these results suggest that cognitive diagnostic models are useful tools for the elaboration of personality profiles based on classifying subjects along binary attributes.

Bayesian Dimensionality Assessment for the Multidimensional Nominal Response Model

This article introduces Bayesian estimation and evaluation procedures for the multidimensional nominal response model. The utility of this model is to perform a nominal factor analysis of items that consist of a finite number of unordered response categories. The key aspect of the model, in comparison with traditional factorial model, is that there is a slope for each response category on the latent dimensions, instead of having slopes associated to the items. The extended parameterization of the multidimensional nominal response model requires large samples for estimation. When sample size is of a moderate or small size, some of these parameters may be weakly empirically identifiable and the estimation algorithm may run into difficulties. We propose a Bayesian MCMC inferential algorithm to estimate the parameters and the number of dimensions underlying the multidimensional nominal response model. Two Bayesian approaches to model evaluation were compared: discrepancy statistics (DIC, WAICC, and LOO) that provide an indication of the relative merit of different models, and the standardized generalized discrepancy measure that requires resampling data and is computationally more involved. A simulation study was conducted to compare these two approaches, and the results show that the standardized generalized discrepancy measure can be used to reliably estimate the dimensionality of the model whereas the discrepancy statistics are questionable. The paper also includes an example with real data in the context of learning styles, in which the model is used to conduct an exploratory factor analysis of nominal data.

Recovery of Weak Factor Loadings When Adding the Mean Structure in Confirmatory Factor Analysis: A Simulation Study

This article extends previous research on the recovery of weak factor loadings in confirmatory factor analysis (CFA) by exploring the effects of adding the mean structure. This issue has not been examined in previous research. This study is based on the framework of Yung and Bentler (1999) and aims to examine the conditions that affect the recovery of weak factor loadings when the model includes the mean structure, compared to analyzing the covariance structure alone. A simulation study was conducted in which several constraints were defined for one-, two-, and three-factor models. Results show that adding the mean structure improves the recovery of weak factor loadings and reduces the asymptotic variances for the factor loadings, particularly for the models with a smaller number of factors and a small sample size. Therefore, under certain circumstances, modeling the means should be seriously considered for covariance models containing weak factor loadings.

Estimación bayesiana de un modelo psicométrico multinivel con efectos aleatorios

El presente estudio aborda la problemática del desarrollo de modelos psicométricos para diseños de investigación multinivel, que tienen como objetivo comparar el nivel medio de los sujetos procedentes de diferentes grupos organizados en niveles definidos de forma jerárquica. Se presenta un modelo psicométrico multinivel basado en la Teoría de Respuesta al Ítem (TRI) y un procedimiento para obtener estimaciones en modelos jerárquicos de TRI mediante métodos bayesianos. El modelo se refiere a datos dicotómicos y un rasgo latente de naturaleza unidimensional, y pone el énfasis en el aspecto jerárquico del análisis. Además de presentar formalmente el modelo, se ilustra su aplicación mediante un ejemplo que incluye datos empíricos referidos a un test de conocimiento matemático aplicado a 1000 estudiantes españoles, organizados en escuelas procedentes de tres regiones. Los resultados proporcionan información sobre cada estudiante, escuela y región. Adicionalmente, se incluye el código de sintaxis empleado para la estimación bayesiana a partir de los programas OpenBUGS y Stan, con el propósito de que el lector pueda adaptar la sintaxis empleada a su propio problema. Finalmente, se discuten las implicaciones del uso de este tipo de modelos multinivel y las posibles líneas de investigación futura.

Anal stretching device for patients with chronic prostatitis and chronic pelvic pain syndrome

OBJECTIVES

Chronic pelvic pain syndrome (CPPS) is a poorly understood and ill-treated condition. It is accompanied by the shortening and increase in tone of the pelvic floor muscles and is closely related to myofascial pain syndrome (MPS). This study aims to evaluate the utility of an anal stretching device (ASD) for improving the pain manifestations of chronic prostatitis (CP) and CPPS.

METHODS

Thirty-one men(38.6 years ± 8.2) were consecutively recruited with an average monitoring period of 14.4 months (± 8.2). The treatment duration was between six months and three years. A clinical history was compiled along with a physical examination and neurophysiological tests. To evaluate pain, the Visual Analogue Scale (VAS) was used before and after treatment; at the final visit, the Clinical Global Impression of Improvement scale (CGI-I) was administered. The ASD is a device that is commercially available in different diameters and lengths.

RESULT

Patients were diagnosed with MPS using neurophysiological tests. Significant differences were found before and after the treatment when evaluating the intensity of the pain using the VAS (6.1±2.1 vs. 1.9±1.3; p < .001). The CGI-I showed a total of 21 patients (70%) whose symptoms were improved or very much improved. Only one patient was worse after the treatment.

CONCLUSIONS

ASD appears to be a safe and useful tool to treat the pain manifestations of CPPS without notable side effects.

Periodicity and patterns of Entamoeba histolytica and E. dispar infection in HIV+/AIDS patients in Mexico

In a 12-month longitudinal study, a cohort of Mexican HIV+/AIDS patients was checked several times for Entamoeba infection, with the parasites identified, as E. histolytica or E. dispar, using PCR. The polymorphic region of the parasites' chitinase genes was investigated by PCR, with the variation in amplicon sizes being used as a measure of the genetic variation among the isolates. The patients found infected with Entamoeba at the start of the study displayed varied patterns of infection clearance and re-infection. The analysis of the polymorphisms in the chitinase gene revealed seven polymorphic patterns in the E. histolytica isolates investigated and three in the E. dispar isolates. Many of the patients were each re-infected with Entamoeba at least once during the 12 months of follow-up. As seen in a previous study in Mexico, none of the E. histolytica-infected patients developed any clinical symptoms of invasive amoebiasis during the follow-up period. The results highlight the complexity of the host-parasite relationship in human amoebiasis.

Extending the CLAST sequential rule to one-way ANOVA under group sampling

Several studies have demonstrated that the fixed-sample stopping rule (FSR), in which the sample size is determined in advance, is less practical and efficient than are sequential-stopping rules. The composite limited adaptive sequential test (CLAST) is one such sequential-stopping rule. Previous research has shown that CLAST is more efficient in terms of sample size and power than are the FSR and other sequential rules and that it reflects more realistically the practice of experimental psychology researchers. The CLAST rule has been applied only to the t test of mean differences with two matched samples and to the chi-square independence test for twofold contingency tables. The present work extends previous research on the efficiency of CLAST to multiple group statistical tests. Simulation studies were conducted to test the efficiency of the CLAST rule for the one-way ANOVA for fixed effects models. The ANOVA general test and two linear contrasts of multiple comparisons among treatment means are considered. The article also introduces four rules for allocating N observations to J groups under the general null hypothesis and three allocation rules for the linear contrasts. Results show that the CLAST rule is generally more efficient than the FSR in terms of sample size and power for one-way ANOVA tests. However, the allocation rules vary in their optimality and have a differential impact on sample size and power. Thus, selecting an allocation rule depends on the cost of sampling and the intended precision.

Effect of Variable and Subject Sampling on Recovery of Weak Factors In CFA

Abstract. Two general issues central to the design of a study are subject sampling and variable sampling. Previous research has examined their effects on factor pattern recovery in the context of exploratory factor analysis. The present paper focuses on recovery of weak factors and reports two simulation studies in the context of confirmatory factor analysis. Conditions investigated include the estimation method (ML vs. ULS), sample size (100, 300, and 500), number of variables per factor (3, 4, or 5), loading size in the weak factor (.25 or .35), and factor correlation (null vs. moderate). Results show that both subject and variable sample size affect the recovery of weak factors, particularly if factors are not correlated. A small but consistent pattern of differences between methods occurs, which favors the use of ULS. Additionally, the frequency of nonconvergent and improper solutions is also affected by the same variables.

[Validation of the cognitive structure of the test of signs by structural equation modeling]

Validation of the cognitive structure of the test of signs by structural equation modeling. The present work is aimed to carry out a validation study of the cognitive operations required for the correct solution of items of a math test which includes basic arithmetic operations between integer numbers. The validation of the hypothesized cognitive structure is made by means of structural equation modeling and triangulation methods. Results show strong and positive cognitive subordination relationships between some items but the structural equation model fit only provides a partial support for the proposed structure. However, the triangulation procedure provides further evidence of validity.

Optimization of sample size in controlled experiments: the CLAST rule

Sequential rules are explored in the context of null hypothesis significance testing. Several studies have demonstrated that the fixed-sample stopping rule, in which the sample size used by researchers is determined in advance, is less practical and less efficient than sequential stopping rules. It is proposed that a sequential stopping rule called CLAST (composite limited adaptive sequential test) is a superior variant of COAST (composite open adaptive sequential test), a sequential rule proposed by Frick (1998). Simulation studies are conducted to test the efficiency of the proposed rule in terms of sample size and power. Two statistical tests are used: the one-tailed t test of mean differences with two matched samples, and the chi-square independence test for twofold contingency tables. The results show that the CLAST rule is more efficient than the COAST rule and reflects more realistically the practice of experimental psychology researchers.

Persistence of secretory antiamoebic antibodies in patients with past invasive intestinal or hepatic amoebiasis

In the present work, it was demonstrated that in amoebic dysentery and amoebic liver abscess patients, the secretory response is long-lasting (> 12 months); and 50% of amoebic dysentery patients developed circulating antiamoebic IgG in comparison with 100% of amoebic liver abscess individuals. A total of 83% of these individuals developed high levels of serum anti-Entamoeba histolytica IgA. However, only 10.4% of the dysentery patients showed this anti-E. histolytica antibody isotype in serum. There was no correlation between secretory and serum antiamoebic response, suggesting independent inductive and effector sites in both compartments.

HLA characterization in adult asymptomatic cyst passers of Entamoeba histolytica/E. dispar

The present work aimed at studying the possible association of HLA antigens with Entamoeba histolytica/E. dispar asymptomatic infection in a Mexican mestizo population. A case-control design was selected for evaluation of the role of genetic markers in parasite infection. For this purpose the HLA-A, HLA-B, and HLA-DR profiles of a population of asymptomatic E. histolytica/E. dispar adult cyst passers (cases) and a corresponding nonparasitized adult group (controls) followed for 12 months were identified. Entamoeba species were identified through zymodeme patterns and/or amplification of species-specific DNA sequences. A healthy, nonparasitized group of individuals was included as a control. Our results show that apparently, no specific HLA marker is associated with the asymptomatic cyst passers' condition. These findings have to be added to previous results in which, in contrast to a demonstrated association between HLA-DR3 and amebic liver abscess in Mexican mestizo adults and infants, no significant association with amebic rectocolitis was found.

The effect of formalin fixation on the polymerase chain reaction characterization of Entamoeba histolytica

Formalin fixation is the most common storage, transportation and preservation method for stool samples. However, fixation dramatically reduces our ability to extract from stool samples DNA that is a suitable template for polymerase chain reaction (PCR)-based diagnostic tests. In this study we evaluated the effects of formalin concentration and of the time stored in fixative on the success of PCR amplification. We found that the deleterious effects of formalin are both time and concentration dependent and may result from fragmentation of fixed DNA during its purification.

Human cell-mediated immune responses to antigenic fractions of Salmonella typhi

The proliferative responses of peripheral blood mononuclear cells of 10 subjects that had typhoid fever, and healthy volunteers without history of typhoid fever or immunization against disease, were analysed with antigen fractions from two protein extracts of Salmonella typhi. Fractions from each extract were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) electrophoresis, transferred to nitrocellulose filters by electroblotting and processed to obtain antigen-bearing nitrocellulose particles for use in lymphocyte cultures. Although the individual proliferative responses were heterogeneous we identified two main immunogenic regions of 29-32 10(3) MW and 45-56 x 10(3) MW for both extracts. Even though there was no one particular antigenic fraction capable of stimulating lymphocytes from all individuals with a previous history of typhoid fever, the combination of three fractions 29-32, 41-45, 63-71 x 10(3) MW could be stimulatory for cells of 90% of these individuals. Also, four subjects that did not respond to unfractionated antigens gave proliferative responses to several fractions of the same extract. We have identified the main immunogenic fractions of S. typhi that might play a role during typhoid infection and postinfection immunity, and merit further purification and characterization.

Cellular immune response to fractionated avian antigens by peripheral blood mononuclear cells from patients with pigeon breeder's disease

Pigeon breeder's disease (PBD), a form of hypersensitivity pneumonitis caused by repeated inhalation of antigens of pigeon origin, is characterized by a diffuse inflammation of the lower respiratory tract. Although a variety of immunologic and nonimmunologic mechanisms have been described in the development of the disease, the pathogenesis is still far from clear. In this study we analyzed the T-lymphocyte proliferative response to a variety of avian antigens with use of peripheral blood mononuclear cells from 11 patients who had PBD and 10 healthy volunteers. We used a new method based on avian antigen-bearing nitrocellulose particles derived from Western blots to study the T-cell proliferative response to 15 antigenic fractions obtained from pigeon serum. With this technique, complex mixtures of antigens can be fractionated by polyacrylamide gel electrophoresis, transferred to nitrocellulose membranes, and used for T-cell proliferation assays with selected antigenic determinants. A wide variety of responses were observed, and there were no reproducible patterns of reaction within either group. Nine of 10 healthy subjects responded to some soluble fractions. However, patients with PBD displayed the strongest response and responded to a significantly greater number of antigenic fractions. Fraction 2, representing a 220 kd molecular weight protein, was the only immunodominant antigen when both groups were compared; it was recognized by 73% of the patients with PBD and by only 20% of control subjects (p < 0.03). These findings show that T lymphocytes of patients with PBD recognize a wide range of bird proteins, which induce marked T-cell proliferation.

Entamoeba histolytica: antibody response to recent and past invasive events

Sero-epidemiological data from endemic amoebiasis areas are difficult to evaluate because the serology of individuals affected by an active process of Entamoeba histolytica tissue invasion is, at present, almost impossible to distinguish from that of individuals who have had an invasive event in the past. The present study compares serum antigenic recognition frequencies among three groups of individuals with different infective conditions: amoebic liver abscess patients; asymptomatic cyst passers; and individuals who have had amoebic liver abscess from one to three years before the study. Control groups consisted of Mexican and Canadian healthy adults. Western blots of E. histolytica membrane extract antigen were reacted with sera from the studied individuals, recognition frequency values were calculated and immunoplots of frequency differences were constructed. The results obtained suggest that the identification and purification of antigenic fractions, which are frequently recognized by sera of amoebic liver abscess patients (136, 132, 93, 70 and 62 kDa), or preferentially associated with past invasive events (144, 140 and 49 kDa), or related to the E. histolytica cyst passer condition (62 and 136 kDa), are important improvements in the use of serology for diagnosis and epidemiological studies in endemic areas of amoebiasis.

Western blot of Entamoeba histolytica antigenic fractions: reactivity analysis with sera from intestinal amoebiasis patients

The reactivity of sera from acute-phase intestinal amoebiasis patients (two weeks evolution) was studied to determine which of the Entamoeba histolytica antigens are most frequently immunogenic. Sera were examined by means of immunoelectrotransferase assay using crude extract of HM1:IMSS E. histolytica trophozoites. Three populations of clinically healthy adults from Mexico, Canada and Germany, with no evidence of parasites in faeces, were used as controls. The frequency of antigen recognition was analysed. In ailing individuals, the bands of 23, 24, 26 and 51 kDa were recognized most frequently (65 and 60%) followed by the 62 kDa band (56%). The combination of some of these bands, namely 3.4, 4.1 and 6.7, with molecular weights of 62, 51 and 24 kDa, increased the recognition frequency of patients to 91.4%. These results constitute a first but important step towards the design of more accurate methods for the successful immunodiagnosis and epidemiology of acute intestinal amoebiasis.

Entamoeba histolytica: specific antigen recognized by a monoclonal antibody

Specific antigenic determinants on the membrane surface of Entamoeba histolytica that distinguish it from other Entamoeba species were demonstrated. Evidence for these antigenic determinants was obtained with a monoclonal antibody to E. histolytica which showed not only specificity but also sensitivity as demonstrated in enzyme linked immunosorbent assay. Immunofluorescence microscopy showed that the monoclonal antibody recognized an epitope present on the membrane surface of E. histolytica trophozoites. The epitope detected by the monoclonal antibody was present in three components of different molecular weight. These components may have a common precursor or may be the result of enzymatic degradation under the conditions tested.

Resistance to Nocardia brasiliensis infection in mice immunized with either Nocardia or BCG

Different vaccination procedures to increase the mechanisms of host resistance to Nocardia brasiliensis were studied in mice. When mice were challenged in the footpad, 2 x 10(8) N. brasiliensis 20 days after footpad inoculation with either viable or killed N. brasiliensis, the mice demonstrated significant resistance to infection when compared with noninfected and nonimmunized mice. The degree of resistance seems to be correlated with the delayed-type hypersensitivity response in the vaccinated animals. Vaccination with another acid-fast bacilli, BCG, afforded both a mild protection and low DTH reactivity. Antibody levels to Nocardia were similar in either Nocardia- or BCG-treated groups indicating that they do not play an important role in resistance to infection by N. brasiliensis.

Changes in host resistance caused by Nocardia brasiliensis in mice: cross-protection against Listeria monocytogenes

Listeria monocytogenes was used to study the rate of development, magnitude, and persistence of the antimicrobial resistance engendered by Nocardia brasiliensis infection in mice. The growth of Listeria in the liver and spleen was more effectively restricted in Nocardia-infected mice than in noninfected animals. The development of delayed-type hypersensitivity to the Nocardia antigen was closely correlated to the increased resistance to Listeria, suggesting that both properties are the consequence of a single immunological event. The antibacterial resistance was also demonstrated in vitro. The results of the foregoing studies indicate that the microbicidal ability of macrophages, very likely activated by cell-mediated immunity, in enhanced in mice infected with Nocardia.