Logistic regression and latent class models for estimating positivities in diagnostic assays with poor resolution

In biomedical research and diagnostic practice it is common to classify objects dichotomously based on continuous observations (x) measuring some form of biological activity, where some proportion of the objects have a level of activity above background. In this paper, we consider the problem of estimating the proportion of positive objects for a typical assay where:(i) the distribution of x for positive objects is unknown. although (ii) the risk of positivity is known to be a monotonic function of x:and (iii) x has been measured for a set of negative control objects. Monte Carlo simulations evaluating four alternative estimators of the positivity, including novel non-parametric mixture decompositions, indicate that where the positives and negatives have distributions of x with a moderate degree of overlap, a non-parametric decomposition using a latent class model provides precise and close to unbiased estimates. The methods are illustrated using data from an autoradiography assay used in cell biology.     

Body Image among Women with Physical Disabilities: Internalization of Norms and Reactions to Nonconformity

Abstract

Body norms for women are based on stereotypical gender expectations regarding physical appearance. Although women in general are exposed to societal standards of the ideal body, women with physical disabilities encounter unique circumstances in meeting these expectations. Women with physical disabilities are often stigmatized because they violate norms of body aesthetics and body shape. This research examines the extent to which women with physical disabilities internalize body norms and the reactions these women have to their nonconformity to societal body standards. In-depth tape-recorded interviews, investigating a variety of social and interpersonal issues, were conducted with 21 female university students with physical disabilities. Using content analysis, the researchers examined the interviews for common themes and patterns relating to body image. The major categories that emerged were (1) awareness of body norms, (2) compliance with body norms, and (3) reactions to nonconformity to body norms. The study illustrates that women with physical disabilities have two general reactions to societal expectations of the ideal female body: emotional responses and stigma management. The lack of questioning of cultural body norms by respondents is discussed as it relates to the rural, small town study location.     

Moving The Mentally Ill Into The Community: The Problem Of Acceptance And The Effect Of Contact

Community acceptance of the mentally ill is fundamental to a successful change to community-based care, now being implemented in New South Wales. This policy was based on an inquiry that viewed acceptance optimistically and postulated that contact with the mentally ill would be a favourable influence. The applicability of this extension of the ‘contact hypothesis’ from its original racial context is tested in one area of Sydney. The results indicate that the type of contact arising from community mental health facilities is not an effective catalyst of relevant attitude change, and suggest particular difficulties among the lower two socioeconomic classes.     

Moving beyond the Janus face of integration and diversity discourses: towards an intersectional framing

This paper proposes the need to move beyond current integration and diversity discourses (and their practices). It argues that whilst purportedly aiming to attack social divisions, on the one hand, these are underpinned by binary and essentialized constructions of these very divisions, on the other. They thereby reinforce notions of ‘us’ and ‘them’. In order to retain their more progressive concerns with heterogeneity and inclusion, the paper brings into focus an intersectional approach that considers the complex and irreducible nature of belonging and social hierarchy. The paper also considers the potential of notions of solidarity and interculturalism in dealing with some of the social issues involved.     

Rethinking social divisions: some notes towards a theoretical framework

This paper attempts to provide a framework for theorising the social divisions of gender, ethnicity and class in terms of parameters of differentiation and inequality which lie at the heart of ‘the social’. The paper argues that there are common parameters to the social divisions of gender, ethnicity’,race’(and class) in terms of categories of difference and positionality. The paper explores the distinctive ontological spaces or domains of gender and ethnos and argues that their study must be undertaken in local and specific contexts paying attention to their articulation. The articulation of the different social processes at the experiential, inter-subjective, organisational and representational levels produces specific social outcomes. Finally, a schematic outline of some of these articulations is presented.     

A BAYESIAN SIMULATION APPROACH TO INFERENCE ON A MULTI‐STATE LATENT FACTOR INTENSITY MODEL

The influence of economic conditions on the movement of a variable between states (for example a change in credit rating from A to B) can be modelled using a multi‐state latent factor intensity framework. Estimation of this type of model is, however, not straightforward, as transition probabilities are involved and the model contains a few highly analytically intractable distributions. In this paper, a Bayesian approach is adopted to manage the distributions. The innovation in the sampling algorithm used to obtain the posterior distributions of the model parameters includes a particle filter step and a Metropolis–Hastings step within a Gibbs sampler. The feasibility and accuracy of the proposed sampling algorithm is supported with a few simulated examples. The paper contains an application concerning what caused 1049 firms to change their credit ratings over a span of ten years.     

Non-stationary partition modeling of geostatistical data for malaria risk mapping

The most common assumption in geostatistical modeling of malaria is stationarity, that is spatial correlation is a function of the separation vector between locations. However, local factors (environmental or human-related activities) may influence geographical dependence in malaria transmission differently at different locations, introducing non-stationarity. Ignoring this characteristic in malaria spatial modeling may lead to inaccurate estimates of the standard errors for both the covariate effects and the predictions. In this paper, a model based on random Voronoi tessellation that takes into account non-stationarity was developed. In particular, the spatial domain was partitioned into sub-regions (tiles), a stationary spatial process was assumed within each tile and between-tile correlation was taken into account. The number and configuration of the sub-regions are treated as random parameters in the model and inference is made using reversible jump Markov chain Monte Carlo simulation. This methodology was applied to analyze malaria survey data from Mali and to produce a country-level smooth map of malaria risk.