Model diagnostic plots for repeated measures data using the generalized estimating equations approach

The generalized estimating equations (GEE) approach has been widely used to analyze repeated measures data. However, in the absence of likelihood ratio tests, model diagnostic checking tools are not well established for the GEE approach, whereas they are for other likelihood-based approaches. Diagnostic checking tools are essential for determining a model's goodness of fit, especially for non-normal data. In this paper, we propose simple residual plots to investigate the goodness of fit of the model based on the GEE approach for discrete data. The proposed residual plots are based on the quantile-quantile (Q-Q) plots of a [chi]2-distribution, and are particularly useful for comparing several models simultaneously.

The Utility of Using Virtue Locales to Explain Criminogenic Environments

Place-based criminology has a long history of examining the potential causes and correlates of criminogenic environments. This line of scholarship has been able to establish that crime, levels of social guardianship, and racial/ethnic groups are unevenly distributed throughout space. Routine activity theory and environmental criminology are two prominent explanations of the causes of criminogenic environments. Specifically, the crime generator and crime attractor scholarship (Brantingham & Brantingham, 1995) has found recent success uncovering which certain land uses that may be “risky facilities” (e.g., pawn shops, payday lenders, bars). However, these paradigms have yet to discover which businesses are crime-reducing and an asset to the communities where they are nested. Thus, the focus of this project is to introduce a new theoretical concept called “virtue locales,” which are race-specific businesses that reduce crime due to their ability to exert high levels of social guardianship. Moreover, other “virtues” they provide are social capital, social cohesion and connections, social ties, and legitimate opportunities to the community. Utilizing various analytic approaches (descriptive buffer analyses, matching techniques, and count regression modeling), this research project tests whether there are crime-reducing associations of proposed virtue locales (e.g., barbershops and beauty salons) on street segments. Findings show that virtue locales are associated with reductions in crime counts, regardless of time of the day. Theoretical implications, policy implications, and a future research agenda will also be presented

The chief digital officer position and its firm-level impact: A literature review on CDO research and an analysis of CDO presence and performance implications

With rapidly advancing technologies and digital innovations, companies face the need to adapt to the new digital world and to digitally transform their business models. For executing the digital transformation process, more and more companies decide to entrust a new C-level manager with all challenges and complexity arising from digital transformation, the Chief Digital Officer (CDO). As the CDO position is still fairly new, research in this field is limited and requires further attention by scholars. Therefore, this study aims to address three fundamental research questions concerning the nature of the CDO position and corresponding implications not only to inform practitioners but also to enrich the scholarly discussion on CDOs. By understanding existing literature on CDOs based on a systematic literature review, this thesis answers the first research question regarding what characterizes the CDO position. Building on these insights and drawing from a comprehensive theoretical framework consisting of upper echelons theory, contingency theory, human capital theory and the resource-based view, hypotheses are developed for answering research questions two and three. While the second research question focuses on factors, which influence CDO presence within a company, the third research question addresses the impact of a CDO on company performance. Based on a large-scale sample of panel data comprised of S&P 500 companies, generalized estimating equations models, propensity score matching and fixed effects regression models are exploited in order to derive answers for both research questions two and three. As influencing factors for CDO presence, the results show that especially early tenure CEOs and CEOs of larger companies are more likely to employ a CDO. Although no evidence can be observed for positive performance implications of CDOs, also given different company contingencies, the insights of this study's analyses show that certain CDO characteristics as well as in combination with CIO presence and varying CEO characteristics are more favorable over others in terms of company performance measured by return on assets and Tobin's Q

Providing hospice care for children: an organizational study

Background: Of the 54,000 children, who die in the US, many lack access to hospice care. As terminally ill children increasingly return home to die, little is known about the hospices that provide care for children and what factors may influence whether care is provided. Objective: To understand the institutional and resource factors that may influence the provision of hospice care for children, while controlling for organizational and market factors. Methods: This study used a retrospective, longitudinal design. The main data source was the California OSHPD -State Utilization Data File of Home Health Agency and Hospice Facilities 2002 to 2008. After applying inclusion and exclusion criteria, the sample size was 1,368 hospice observations over 7 years. Drawing on institutional and resource dependence theory, this study used generalized estimating equations to examine the institutional and resource pressures associated with provision of hospice care. Interaction terms were included to assess the moderating effect of resource pressures on the relationship between institutional pressures and provision of care. Results: The percentage of hospices providing care for children significantly declined from 2002 to 2008. This study found that provision of hospice care for children was positively associated with membership in a professional group, and was negatively related to small-sized hospice, medium-sized hospices, and increasing competition. There was no effect of accreditation, organization leader, or other income on providing pediatric hospice care. In addition, small size attenuated the accreditation-provision relationship and medium size magnified the membership-provision relationship. Conclusions: The findings of this study provide specific information on the institutional and resource pressures exerted on hospices in the provision of care for children, and suggests organizational and policy level strategies to improve access to and delivery of hospice care for children

Weather impact on trip generation and modal split

Vremenski uslovi su uglavnom izostavljeni iz istraživanja o transportnim zahtevima ili su razmatrani na pojednostavljen način sve do kraja devedesetih godina prošlog veka. U odnosu na broj radova koji istražuju uticaj vremenskih uslova na saobraćajnu infrastrukturu, ponašanje vozača i bezbednost saobraćaja, znatno manji broj radova bavi se uticajem vremenskih uslova na transportne zahteve. Poslednjih godina uticaj klimatskih i promena vremenskih uslova, kao strateški važne teme na globalnom nivou, postaju važne teme i u oblasti planiranja saobraćaja. Upravo u poslednjih nekoliko godina uočen je veliki porast interesovanja za istraživanje uticaja vremenskih uslova na karakteristike transportnih zahteva. Osnovna hipoteza doktorske disertacije jeste da vremenski uslovi utiču na karakteristike kretanja i da se taj uticaj može kvantifikovati. U okviru doktorske disertacije razvijena je metodologija istraživanja uticaja vremenskih uslova na nastajanje i vidovnu raspodelu putovanja i predstavljen je postupak modeliranja nastajanja i vidovne raspodele putovanja u različitim vremenskim uslovima. Metodologija podrazumeva sprovođenje istraživanja metodom „izjavljenih prilagođavanja“, a ukoliko rezultati pokažu opravdanost, istraživanja se sprovode i metodom „izraženih preferencija“, u cilju utvrđivanja realnih promena karakteristika kretanja u različitim vremenskim uslovima. Metodologija se oslanja na savremene načine prikupljanja podataka, za koje se pokazalo da su pouzdani naročito u slučaju ponovljenih merenja. Razvijeni su modeli uticaja vremenskih uslova na nastajanje i vidovnu raspodelu putovanja, koji pored uticaja vremenskih uslova uključuju i socio-ekonomske karakteristike pojedinca. Razvijena metodologija je testirana na primeru zaposlenih stanovnika Beograda...Weather impact is usually omitted or considered simplistically in transport demand studies until the end of the nineties. Considerably smaller number of papers deals with the weather impact on the transport demand in comparison with papers that explore weather impact on road infrastructure, driver behavior and traffic safety. The impact of climate change and weather change, as strategically important topics at the global level, also become important topics in the field of transportation planning in recent years. Increased interest in weather impact on transport demand has been seen in the last few years. The basic hypothesis in the doctoral dissertation is that weather affects travel behavior and that this effect can be quantified. Research methodology for weather impact on trip generation and modal split and method for trip generation and modal split modelling in different weather conditions are provided in this doctoral thesis. The methodology involves research based on “stated adaptation” method and if the results show statistical significant difference between the scenarios research would be carried out based on “revealed preferences” method in order to determine the real travel behavior change in different weather conditions. The methodology relies on modern data collection methods that have been proven as reliable, especially in the case of repeated measurements. Modelling procedure for weather impact on trip generation and modal split, that includes individual’s socio-economic characteristics in addition to the weather impact, was developed. Developed methodology was tested on employees in Belgrade..

Investigating the use of medicines in management of children and young people with epilepsy using data from primary care in the UK

Background: Epilepsy is a serious chronic neurological disorder that has a higher incidence in children and young people (CYP) than in adults. Epilepsy negatively impacts physical and psychosocial quality of life of CYP. Good outcomes of epilepsy are associated with optimal choice of drug treatment and adequate adherence to the prescribed medicines. Research on the patterns of medication use and adherence to prescribed medicines in CYP remains limited. The long-term clinical outcomes and costs of treating epilepsy have not been extensively studied in CYP in the UK. Aim of the study: This thesis aimed to investigate the pattern of antiepileptic drug (AED) prescribing and the dynamic of medication adherence in CYP with epilepsy. The long-term clinical outcomes and direct costs of treating epilepsy in CYP were estimated at population level. Methods: This study is an observational cohort study of CYP, age 0-17 years, identified from The Health Improvement Network (THIN) primary care database from the UK between January 1988 and December 2004. Four different analyses were carried out on this cohort. First, a cross-sectional design repeated annually was employed to estimate the incidence and prevalence of epilepsy and the pattern of AED prescribing in this population. Secondly, the long-term adherence to prescribed AEDs was calculated using the medication possession ratio (MPR) method. Applying panel data analysis and the Generalised Estimating Equation (GEE) multivariate regression, factors that may have been associated with adherence to the prescribed AEDs were examined. Thirdly, seizure outcomes in terms of seizure frequency and remission of seizures and potential associated factors were assessed using the method of multiple failure survival analysis. Finally, the direct costs of treating epilepsy in CYP in primary care were estimated and stratified by the number of years after the first recording of epilepsy in THIN data. Results: Of total 528,760 CYP born on or after 1st January 1988 and registered in general practices contributed to THIN until 31st December 2004, 2020 CYP were identified who had a diagnosis of epilepsy, from under 1 up to 16.3 years of age (mean=5.6; SD=4.1). The annual incidence of epilepsy in CYP stratified by calendar years ranged from 44.4 (95% CI=31.9-61.8) to 61.2 (95% CI=50.6 -74.1) per 100,000 person-years. Incidence of epilepsy was significantly higher in children with greater socioeconomic deprivation than those with lower deprivation. Around 60% of CYP with epilepsy were prescribed monotherapy each year. Old AEDs such as carbamazepine and sodium valproate were the most frequently prescribed drugs and often prescribed as monotherapy to control epilepsy throughout 1990-2003. Prescribing of lamotrigine, a new AED, increased from 0.07 per person-years in 1992 to 2 per person-years in 2003. The calculated annual adherence to AEDs showed that around 50% of CYP adhered to at least 80% of the prescribed medications each year. Demographic characteristics of CYP were of little significance to affect adherence levels. The incidence of seizures was 0.73 (95% CI=0.71-0.75) per person-years. Incidence of seizures was higher in younger children up to 2 years and decreased with increasing age. A proportion of 94% (95% CI=93%, 96%) of CYP achieved 1 year remission of seizures, 80% (95% CI= 78%, 83%) achieved 2 years and 47% (95% CI=43%, 50%) achieved 5 years remission of seizures. The mean total direct cost associated with treating epilepsy in CYP, according to information in the general practice records that also indicated specialist and hospital care, was estimated at £ 1,153 (SD=1,808) per child in the first year following epilepsy diagnosis and at £459 (SD=1,633) per child for subsequent years. The costs of hospital care and AEDs represented the highest contribution to the total direct costs of epilepsy. The annual direct cost was significantly higher in younger children up to 2 years old. No significant difference in the annual costs was observed between CYP who adhered to at least 80% of medications and those who adhered to less than 80%. Conclusions: The incidence of epilepsy was highest in young children and CYP of higher socioeconomic deprivation. Old AEDs were most often prescribed as first-line drugs and as monotherapy to control epilepsy. Of newer AEDs, there was an increasing trend of prescribing lamotrigine and topiramate as add-on therapy. Long-term adherence to prescribed AEDs was suboptimal in one-half of CYP and positively associated with higher seizure frequency. Inpatient hospital care and drugs were the major contributors to the direct costs of treating epilepsy in CYP. Non-adherence to prescribed medicines was associated with higher hospital care costs but not with total direct costs as the medicines themselves made large contribution to the direct cost