Recognizing Structural Nonidentifiability: When Experiments Do Not Provide Information About Important Parameters and Misleading Models Can Still Have Great Fit

In the quest to model various phenomena, the foundational importance of parameter identifiability to sound statistical modeling may be less well appreciated than goodness of fit. Identifiability concerns the quality of objective information in data to facilitate estimation of a parameter, while nonidentifiability means there are parameters in a model about which the data provide little or no information. In purely empirical models where parsimonious good fit is the chief concern, nonidentifiability (or parameter redundancy) implies overparameterization of the model. In contrast, nonidentifiability implies underinformativeness of available data in mechanistically derived models where parameters are interpreted as having strong practical meaning. This study explores illustrative examples of structural nonidentifiability and its implications using mechanistically derived models (for repeated presence/absence analyses and dose–response of Escherichia coli O157:H7 and norovirus) drawn from quantitative microbial risk assessment. Following algebraic proof of nonidentifiability in these examples, profile likelihood analysis and Bayesian Markov Chain Monte Carlo with uniform priors are illustrated as tools to help detect model parameters that are not strongly identifiable. It is shown that identifiability should be considered during experimental design and ethics approval to ensure generated data can yield strong objective information about all mechanistic parameters of interest. When Bayesian methods are applied to a nonidentifiable model, the subjective prior effectively fabricates information about any parameters about which the data carry no objective information. Finally, structural nonidentifiability can lead to spurious models that fit data well but can yield severely flawed inferences and predictions when they are interpreted or used inappropriately.     

Citing history

ABSTRACT

Although rarely considered within the existing scholarship on social movements, even a cursory analysis of protest activity suggests that movements regularly invoke historical citations (whether consciously or not) while working to clarify aims and mobilize constituencies. In order to make sense of this process, and to account for the variations that arise among the different citation modalities favored by movements on opposite ends of the political spectrum, I draw upon the theoretical contributions of Marxist cultural critic Walter Benjamin and, in particular, on his exploration of ‘wish images’ and ‘dialectical images,’ their attributes, and their interrelationship. According to Benjamin, such images summoned the past either to project visions of future happiness (as with the wish image) or to deposit the witness before a moment of decisive, present-tense reckoning. After outlining the role of historical citation in social movements and in the broader cultural field through which these movements find expression, I analyze two recent protest events – the ‘Unite the Right’ rally in Charlottesville, VA, in which wish images were actively deployed, and the 2017 Women’s Strike in New York City, where a dialectical image arose from the constellated nodes of the march’s route – to consider the relationship between citation modality and protest outcome. Following from this analysis, and in keeping with the unapologetically partisan nature of my investigation, I conclude by advancing some strategic recommendations for movements seeking – as Benjamin once enjoined – to ‘improve our position in the struggle against Fascism.’     

Disabled or differently-enabled? Dyslexic identities in online forum postings

This study presents a novel exploration into how people with dyslexia construct personal identities within anonymous, unsolicited, postings to an online discussion forum. An interpretational phenomenological analysis suggested three key identities: learning-disabled, differently-enabled and societally-disabled. These are discussed in terms of the extent to which they draw differentially on a discourse of disability as opposed to one of individual difference. The identities are to an extent malleable and overlapping according to context. Postings suggested overall that while some contributors constructed themselves as differently-enabled and celebrated dyslexia-related abilities, others sensed themselves having a disabled identity imposed upon them. Dyslexia is perceived as negatively construed within a society which promotes literacy and cognitive acuity as essential aspects of educational and social competence and where learning differences are poorly tolerated. In addition, this study highlights the potential of online forum contributions in the study of social influences in under-researched groups.     

Teaching Children With Autism Spectrum Disorder to Report Past Behavior With the Use of a Speech-Generating Device

The Analysis of Verbal Behavior -     

Filmic public relations for a global audience: The United Nations and The Blue Vanguard

The project investigates the use of documentary film as a public relations tool by the United Nations (UN) for worldwide promotion of its first peacekeeping intervention in response to the Suez crisis of 1956. Specifically, it undertakes a historical investigation into the communicative purpose of the 1957 documentary film, The Blue Vanguard, which was made by the UN Department of Public Information (UNDPI). Beyond the interest connected with the intervention in the Suez crisis, the film is significant in the history of the UN’s global public relations since it was one of the first films made for the UN by UK film director, Thorold Dickinson, who arrived as Chief of Film at the UN in October 1956.The author argues that Thorold Dickinson used the documentary to make a radical public information proposition to a global audience on behalf of the United Nations. Specifically, the public relations discourse and cinematicity in The Blue Vanguard reminded a global audience that achieving peace required a new level of cultural tolerance and global co-operation, involving codes of judgement beyond the nationalistically-determined registers of the time.     

Risk Detection and Self‐Protection Among Homeless Youth

Utilizing qualitative interviews with a large sample of 145 homeless youth seeking services at homeless youth service agencies from across three U.S. cities (Los Angeles, Denver, and Austin), this study sought to explore youths' perspectives on ways in which they detect risk and protect themselves on the streets. Results indicated that youth use a combination of internal cues (affective responses) and external cues (reading people) to detect danger, although many times danger was described as undetectable. Certain contexts, includes those that were unfamiliar, difficult to escape, or involved drugs were described as most dangerous. In response to these dangers, youth employed self‐protection strategies such as carrying weapons, banding together with trusted others, isolating, or seeking programing to leave the streets.     

Factors Associated With Substance Use Disorders Among Traumatized Homeless Youth

This study aimed to identify homeless youths’ lifestyle and trauma-related risk factors as well as protective factors associated with alcohol use disorder or no disorder and drug use disorder or no disorder. Youth receiving homeless services in Denver (n = 201), Austin (n = 200), and Los Angeles (n = 200; N = 601) completed quantitative interviews assessing demographic information, alcohol and drug use, homeless lifestyle risk factors, trauma-related risk factors, and protective factors. Findings showed differences in trauma-related risk factors between alcohol and drug use disorders, but not homeless lifestyle risks. Protective factors predicted substance use disorders beyond risk factors. Understanding trauma-related risk and protective factors associated with substance use disorders could improve interventions.