Irini Moustaki | London School of Economics and Political Science (original) (raw)

Papers by Irini Moustaki

Springer proceedings in mathematics & statistics, 2023

In disease control or elimination programs, diagnostics are essential for assessing the impact of... more In disease control or elimination programs, diagnostics are essential for assessing the impact of interventions, refining treatment strategies, and minimizing the waste of scarce resources. Although high-performance tests are desirable, increased accuracy is frequently accompanied by a requirement for more elaborate infrastructure, which is often not feasible in the developing world. These challenges are pertinent to mapping, impact monitoring, and surveillance in trachoma elimination programs. To help inform rational design of diagnostics for trachoma elimina-tion, we outline a nonparametric multilevel latent Markov modeling approach and apply it to 2 longitudinal cohort studies of trachoma-endemic communities in Tanzania (2000–2002) and The Gambia (2001–2002) to provide simultaneous inferences about the true population prevalence of Chlamydia trachomatis infection and disease and the sensitivity, specificity, and predictive values of 3 diagnostic tests for C. trachomatis infection...

PLOS Neglected Tropical Diseases, 2021

Various global health initiatives are currently advocating the elimination of schistosomiasis wit... more Various global health initiatives are currently advocating the elimination of schistosomiasis within the next decade. Schistosomiasis is a highly debilitating tropical infectious disease with severe burden of morbidity and thus operational research accurately evaluating diagnostics that quantify the epidemic status for guiding effective strategies is essential. Latent class models (LCMs) have been generally considered in epidemiology and in particular in recent schistosomiasis diagnostic studies as a flexible tool for evaluating diagnostics because assessing the true infection status (via a gold standard) is not possible. However, within the biostatistics literature, classical LCM have already been criticised for real-life problems under violation of the conditional independence (CI) assumption and when applied to a small number of diagnostics (i.e. most often 3-5 diagnostic tests). Solutions of relaxing the CI assumption and accounting for zero-inflation, as well as collecting part...

Metron-International Journal of Statistics, Jul 30, 2015

Composite likelihood estimation has been proposed in the literature for handling intractable like... more Composite likelihood estimation has been proposed in the literature for handling intractable likelihoods. In particular, pairwise likelihood estimation has been recently proposed to estimate models with latent variables and random effects that involve high dimensional integrals. Pairwise estimators are asymptotically consistent and normally distributed but not the most efficient among consistent estimators. Vasdekis et al. (Biostatistics 15:677–689, 2014) proposed a weighted estimator that is found to be more efficient than the unweighted pairwise estimator produced by separate maximizations of pairwise likelihoods. In this paper, we propose a modification to that weighted estimator that leads to simpler computations and study its performance through simulations and a real application.

Springer Proceedings in Mathematics & Statistics, 2021

This article studies the power of the Lagrange Multiplier Test and the Generalized Lagrange Multi... more This article studies the power of the Lagrange Multiplier Test and the Generalized Lagrange Multiplier Test to detect measurement non-invariance in Item Response Theory (IRT) models for binary data. We study the performance of these two tests under correct model specification and incorrect distribution of the latent variable. The asymptotic distribution of each test under the alternative hypothesis depends on a noncentrality parameter that is used to compute the power. We present two different procedures to compute the noncentrality parameter and consequently the power of the tests. The performance of the two methods is evaluated through a simulation study. They turn out to be very similar to the classic empirical power but less time consuming. Moreover, the results highlight that the Lagrange Multiplier Test is more powerful than the Generalized Lagrange Multiplier Test to detect measurement noninvariance under all simulation conditions.

British Journal of Mathematical and Statistical Psychology, 2021

This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

LSE Public Policy Review, 2021

Families extend well beyond households. In particular, connections between parents and their adul... more Families extend well beyond households. In particular, connections between parents and their adult offspring are often close and sustained, and transfers may include financial assistance, practical support, or both, provided by either generation to the other. Yet this major engine of welfare production, distribution, and redistribution has only recently become the focus of research. Who are the beneficiaries and to what extent are the patterns of exchange socially stratified? This article discusses findings from a programme of research analysing data from two nationally representative longitudinal studies, the British Household Panel Study and its successor Understanding Society, which record help given by, and received by, respondents through exchanges with their non-coresident parents and offspring in the UK. Some families exhibit a high tendency to provide mutual support between generations; these tendencies persist over time. Financial and practical support are generally complementary rather than substitutes. Longer travel time between parents and their offspring makes the provision of practical help less likely, whilst social class, social mobility, and ethnicity exhibit complex patterns of association with intergenerational exchanges. The resulting conclusion is that exchanges within families are an important complement to formal welfare institutions in the UK and that social policies should be designed to work with the grain of existing patterns of exchange, enabling family members to continue to provide help to one another, but ensuring that those who are less well supported by intergenerational assistance can access effective social protection.

Journal of the Royal Statistical Society Series A: Statistics in Society, 2020

Summary We propose a multilevel structural equation model to investigate the interrelationships b... more Summary We propose a multilevel structural equation model to investigate the interrelationships between childhood socio-economic circumstances, partnership formation and stability, and mid-life health, using data from the 1958 British birth cohort. The structural equation model comprises latent class models that characterize the patterns of change in four dimensions of childhood socio-economic circumstances and a joint regression model that relates these categorical latent variables to partnership transitions in adulthood and mid-life health, while allowing for informative dropout. The model can be extended to handle multiple outcomes of mixed types and at different levels in a hierarchical data structure.

Psychometrika, 2016

Correlated multivariate ordinal data can be analysed with structural equation models. Parameter e... more Correlated multivariate ordinal data can be analysed with structural equation models. Parameter estimation has been tackled in the literature using limited-information methods including three-stage least squares and pseudo-likelihood estimation methods such as pairwise maximum likelihood estimation. In this paper, two likelihood ratio test statistics and their asymptotic distributions are derived for testing overall goodness-of-fit and nested models respectively under the estimation framework of pairwise maximum likelihood estimation. Simulation results show a satisfactory performance of type I error and power for the proposed test statistics and also suggest that the performance of the proposed test statistics is similar to that of the test statistics derived under the three-stage diagonally weighted and unweighted least squares. Furthermore, the corresponding, under the pairwise framework, model selection criteria, AIC and BIC, show satisfactory results in selecting the right model in our simulation examples. The derivation of the likelihood ratio test statistics and model selection criteria under the pairwise framework together with pairwise estimation provide a flexible framework for fitting and testing structural equation models for ordinal as well as for other types of data. The test statistics derived and the model selection criteria are used on data on 'trust in the police' selected from the 2010 European Social Survey. The proposed test statistics and the model selection criteria have been implemented in the R package lavaan 1 .

SSRN Electronic Journal, 2016

When missing data are produced by a non-ignorable nonresponse mechanism, analysis of the observed... more When missing data are produced by a non-ignorable nonresponse mechanism, analysis of the observed data should include a model for the probabilities of responding. In this paper we propose such models for nonresponse in survey questions which are treated as multiple-item measures of latent constructs and analysed using latent variable models. The nonresponse models that we describe include additional latent variables (latent response propensities) which determine the response probabilities. We argue that this model should be specified as flexibly as possible, and propose models where the response propensity is a categorical variable (a latent response class). This can be combined with any latent variable model for the survey items themselves, and an association between the latent variables measured by the items and the latent response propensities implies a model with non-ignorable nonresponse. We consider in particular the analysis of data from cross-national surveys, where the nonresponse model may also vary across the countries. The models are applied to analyse data on welfare attitudes in 29 countries in the European Social Survey.

Journal of the Royal Statistical Society: Series A (Statistics in Society), 1999

This paper proposes a new approach to the treatment of item non-response in attitude scales. It c... more This paper proposes a new approach to the treatment of item non-response in attitude scales. It combines the ideas of latent variable identi®cation with the issues of non-response adjustment in sample surveys. The latent variable approach allows missing values to be included in the analysis and, equally importantly, allows information about attitude to be inferred from nonresponse. We present a symmetric pattern methodology for handling item non-response in attitude scales. The methodology is symmetric in that all the variables are given equivalent status in the analysis (none is designated a`dependent' variable) and is pattern based in that the pattern of responses and non-responses across individuals is a key element in the analysis. Our approach to the problem is through a latent variable model with two latent dimensions: one to summarize response propensity and the other to summarize attitude, ability or belief. The methodology presented here can handle binary, metric and mixed (binary and metric) manifest items with missing values. Examples using both arti®cial data sets and two real data sets are used to illustrate the mechanism and the advantages of the methodology proposed.

... Proceedings of the American Statistical Assocation, Section of Survey Research Methods Sectio... more ... Proceedings of the American Statistical Assocation, Section of Survey Research Methods Section. Item Type: Conference or Workshop Item (Paper). Official URL: http://www.amstat.org/Sections/Srms/Proceedings/. Additional Information: © 1996 American Statistical Assocation. ...

Educational and Psychological Measurement, 2021

This article studies the Type I error, false positive rates, and power of four versions of the La... more This article studies the Type I error, false positive rates, and power of four versions of the Lagrange multiplier test to detect measurement noninvariance in item response theory (IRT) models for binary data under model misspecification. The tests considered are the Lagrange multiplier test computed with the Hessian and cross-product approach, the generalized Lagrange multiplier test and the generalized jackknife score test. The two model misspecifications are those of local dependence among items and nonnormal distribution of the latent variable. The power of the tests is computed in two ways, empirically through Monte Carlo simulation methods and asymptotically, using the asymptotic distribution of each test under the alternative hypothesis. The performance of these tests is evaluated by means of a simulation study. The results highlight that, under mild model misspecification, all tests have good performance while, under strong model misspecification, the tests performance deter...

When four of the leading researchers in the field of quantitative social sciences team up to writ... more When four of the leading researchers in the field of quantitative social sciences team up to write a book together, you can expect nothing less than a brilliant work. That is what the first edition of “Analysis of Multivariate Social Science Data ” from 2002 was, and that’s what the current second edition is. This new edition contains additional chapters on regression analysis, confirmatory factor analysis including structural equation models, and multilevel models. The strength of this book lies in the right mixture of simple mathematical expressions, com-prehensive non-mathematical descriptions of various multivariate approaches, numerous in-teresting real-life data examples (almost half of each chapter is dedicated to examples), and, last but not least, detailed interpretation of the results. As in other Bartholomew books, well-known methods or certain parts of them are, in many cases, presented from a slightly different angle. This makes this book also interesting for experience...

Tests are a building block of our modern education system. Many tests are high-stake, such as adm... more Tests are a building block of our modern education system. Many tests are high-stake, such as admission, licensing, and certification tests, that can significantly change one's life trajectory. For this reason, ensuring fairness in educational tests is becoming an increasingly important problem. This paper concerns the issue of item preknowledge in educational tests due to item leakage. That is, a proportion of test takers have access to leaked items before a test is administrated, which leads to inflated performance on the set of leaked items. We develop methods for the simultaneous detection of cheating test takers and compromised items based on data from a single test administration, when both sets are completely unknown. Latent variable models are proposed for the modelling of (1) data consisting only of item-level binary scores and (2) data consisting of both item-level binary scores and response time, where the former is commonly available in paper-and-pencil tests and the...

Medicine, 2017

The aim of the present study was to identify the sexual behavior, attitudes, beliefs, and knowled... more The aim of the present study was to identify the sexual behavior, attitudes, beliefs, and knowledge on sexually transmitted infections (STIs) focused on human papilloma virus (HPV) in the Greek adolescent population. The participants were 4547 adolescents, a representative sample for Greek territory with a mean age of 17 years. After written permission from Greek ministry of education each student completed a questionnaire with 36 questions. The fields covered were demographic characteristics, sexual life data, and basic knowledge on HPV. In the present study, 43% and 75% of the participants knew about HPV or cervical cancer, while more than 6 out of 10 did not know the association between the 2. More than 60% of the participants could not answer correctly neither about HPV infection and cervical cancer frequency in sexually active women, nor about protection methods against HPV and cervical cancer. This study shows that the low vaccination coverage of the Greek population may be due to lack of information and awareness of the adolescents and their parents. It is our duty to increase our efforts in order to better educate the population and vaccinate the population as early as possible in their reproductive years. Abbreviations: HPV = human papilloma virus, STI = sexually transmitted infection.

Research Synthesis Methods, 2016

Detecting outlying studies in meta-regression models using a forward search algorithm. Research S... more Detecting outlying studies in meta-regression models using a forward search algorithm. Research Synthesis Methods, 8 (2). pp. 199-211.

Latent class models are used in social sciences for classifying individuals or objects into disti... more Latent class models are used in social sciences for classifying individuals or objects into distinct groups/classes based on responses to a set of observed indicators. The latent class model for mixed binary and metric variables (Br. J. Math. Statist. Psych. 49 (1996) 313) is extended to accommodate any type of data (including ordinal and nominal) and its use in Archaeometry for classifying archaeological findings/objects into groups is discussed. The models proposed are estimated using a full maximum like-lihood with the EM algorithm. Two data sets from archaeological findings are used to illustrate the methodology.