A marginalized two-part model for semicontinuous data

2014 ◽  
Vol 33 (28) ◽  
pp. 4891-4903 ◽  
Author(s):  
Valerie A. Smith ◽  
John S. Preisser ◽  
Brian Neelon ◽  
Matthew L. Maciejewski
Keyword(s):  
Semicontinuous Data ◽  
Part Model

scholarly journals Analysis of longitudinal semicontinuous data using marginalized two-part model

2018 ◽  
Vol 16 (1) ◽  
Author(s):  
Miran A. Jaffa ◽  
Mulugeta Gebregziabher ◽  
Sara M. Garrett ◽  
Deirdre K. Luttrell ◽  
Kenneth E. Lipson ◽  
...  
Keyword(s):  
Semicontinuous Data ◽  
Part Model

A marginalized two-part model for longitudinal semicontinuous data

2015 ◽  
Vol 26 (4) ◽  
pp. 1949-1968 ◽  
Author(s):  
Valerie A Smith ◽  
Brian Neelon ◽  
John S Preisser ◽  
Matthew L Maciejewski
Keyword(s):  
Health Care ◽  
Health Services ◽  
Random Effect ◽  
Continuous Distribution ◽  
Health Care Expenditures ◽  
Health Services Use ◽  
Services Research ◽  
Population Mean ◽  
Semicontinuous Data ◽  
Part Model

In health services research, it is common to encounter semicontinuous data, characterized by a point mass at zero followed by a right-skewed continuous distribution with positive support. Examples include health expenditures, in which the zeros represent a subpopulation of patients who do not use health services, while the continuous distribution describes the level of expenditures among health services users. Longitudinal semicontinuous data are typically analyzed using two-part random-effect mixtures with one component that models the probability of health services use, and a second component that models the distribution of log-scale positive expenditures among users. However, because the second part conditions on a non-zero response, obtaining interpretable effects of covariates on the combined population of health services users and non-users is not straightforward, even though this is often of greatest interest to investigators. Here, we propose a marginalized two-part model for longitudinal data that allows investigators to obtain the effect of covariates on the overall population mean. The model additionally provides estimates of the overall population mean on the original, untransformed scale, and many covariates take a dual population average and subject-specific interpretation. Using a Bayesian estimation approach, this model maintains the flexibility to include complex random-effect structures and easily estimate functions of the overall mean. We illustrate this approach by evaluating the effect of a copayment increase on health care expenditures in the Veterans Affairs health care system over a four-year period.

scholarly journals Two-part models with stochastic processes for modelling longitudinal semicontinuous data: Computationally efficient inference and modelling the overall marginal mean

2017 ◽  
Vol 27 (12) ◽  
pp. 3679-3695 ◽  
Author(s):  
Sean Yiu ◽  
Brian DM Tom
Keyword(s):  
Distribution Function ◽  
Stochastic Processes ◽  
Cumulative Distribution Function ◽  
Marginal Likelihood ◽  
Cumulative Distribution ◽  
Patient Specific ◽  
High Dimensional ◽  
Multivariate Normal ◽  
Semicontinuous Data ◽  
Part Model

Several researchers have described two-part models with patient-specific stochastic processes for analysing longitudinal semicontinuous data. In theory, such models can offer greater flexibility than the standard two-part model with patient-specific random effects. However, in practice, the high dimensional integrations involved in the marginal likelihood (i.e. integrated over the stochastic processes) significantly complicates model fitting. Thus, non-standard computationally intensive procedures based on simulating the marginal likelihood have so far only been proposed. In this paper, we describe an efficient method of implementation by demonstrating how the high dimensional integrations involved in the marginal likelihood can be computed efficiently. Specifically, by using a property of the multivariate normal distribution and the standard marginal cumulative distribution function identity, we transform the marginal likelihood so that the high dimensional integrations are contained in the cumulative distribution function of a multivariate normal distribution, which can then be efficiently evaluated. Hence, maximum likelihood estimation can be used to obtain parameter estimates and asymptotic standard errors (from the observed information matrix) of model parameters. We describe our proposed efficient implementation procedure for the standard two-part model parameterisation and when it is of interest to directly model the overall marginal mean. The methodology is applied on a psoriatic arthritis data set concerning functional disability.

A marginalized two-part model with heterogeneous variance for semicontinuous data

2018 ◽  
Vol 28 (5) ◽  
pp. 1412-1426
Author(s):  
Valerie A Smith ◽  
John S Preisser
Keyword(s):  
Continuous Distribution ◽  
Health Care Expenditures ◽  
Positive Outcome ◽  
Behavioral Weight Loss ◽  
Modeling Framework ◽  
Constant Variance ◽  
Behavioral Weight Loss Intervention ◽  
Semicontinuous Data ◽  
Log Normal ◽  
Part Model

Semicontinuous data, characterized by a point mass at zero followed by a positive, continuous distribution, arise frequently in medical research. These data are typically analyzed using two-part mixtures that separately model the probability of incurring a positive outcome and the distribution of positive values among those who incur them. In such a conditional specification, however, standard two-part models do not provide a marginal interpretation of covariate effects on the overall population. We have previously proposed a marginalized two-part model that yields more interpretable effect estimates by parameterizing the model in terms of the marginal mean. In the original formulation, a constant variance was assumed for the positive values. We now extend this model to a more general framework by allowing non-constant variance to be explicitly modeled as a function of covariates, and incorporate this variance into two flexible distributional assumptions, log-skew-normal and generalized gamma, both of which take the log-normal distribution as a special case. Using simulation studies, we compare the performance of each of these models with respect to bias, coverage, and efficiency. We illustrate the proposed modeling framework by evaluating the effect of a behavioral weight loss intervention on health care expenditures in the Veterans Affairs health system.

scholarly journals Health and Housing Energy Expenditures: A Two-Part Model Approach

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 943
Author(s):  
Fátima Lima ◽  
Paula Ferreira ◽  
Vítor Leal
Keyword(s):  
Low Income ◽  
Health Expenditures ◽  
Household Level ◽  
Energy Expenditures ◽  
Health And Wellbeing ◽  
Health Gains ◽  
Key Factor ◽  
Using Data ◽  
Part Model ◽  
Model Approach

Interest in the interaction between energy and health within the built environment has been increasing in recent years, in the context of sustainable development. However, in order to promote health and wellbeing across all ages it is necessary to have a better understanding of the association between health and energy at household level. This study contributes to this debate by addressing the case of Portugal using data from the Household Budget Survey (HBS) microdata database. A two-part model is applied to estimate health expenditures based on energy-related expenditures, as well as socioeconomic variables. Additional statistical methods are used to enhance the perception of relevant predictors for health expenditures. Our findings suggest that given the high significance and coefficient value, energy expenditure is a relevant explanatory variable for health expenditures. This result is further validated by a dominance analysis ranking. Moreover, the results show that health gains and medical cost reductions can be a key factor to consider on the assessment of the economic viability of energy efficiency projects in buildings. This is particularly relevant for the older and low-income segments of the population.

scholarly journals Association between fasting insulin and C-reactive protein among adults without diabetes using a two-part model: NHANES 2005–2010

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Amanda L. Missel ◽  
Laura R. Saslow ◽  
Dina H. Griauzde ◽  
Donna Marvicsin ◽  
Ananda Sen ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Waist Circumference ◽  
Low Grade ◽  
Fasting Insulin ◽  
C Reactive Protein ◽  
Glucose Levels ◽  
Reactive Protein ◽  
Part Model

Abstract Introduction Chronic inflammation is associated with the development, progression and long-term complications of type 2 diabetes. Hyperglycemia is associated with chronic low-grade inflammation, and thus has become the focus of many screening and treatment recommendations. We hypothesize that insulin may also be associated with inflammation and may be an additional factor to consider in screening and treatment. Methods This study used National Health and Nutrition Examination Survey data from 2005 to 2010 to analyze the association between fasting insulin and C-reactive protein (CRP). A two-part model was used due to the high number of values reported as 0.1 mg/L. Two models were analyzed, both with and without the addition of waist circumference to other covariates in the model. Results The final sample included 4527 adults with a mean age of 43.31 years. In the first model, higher fasting insulin was associated with increased odds of CRP > 0.1 mg/L (OR = 1.02, p < .001) and with higher CRP (β = 0.03, p < .001). In the adjusted model, including waist circumference as a covariate, higher fasting insulin was not associated with CRP > 0.1 mg/L (OR = 1.00, p = .307) but the association between higher fasting insulin and higher continuous CRP remained significant (β = 0.01, p = .012). Conclusion This study found that higher fasting insulin is associated with higher CRP. These results suggest that treatment approaches that simultaneously decrease insulin levels as well as glucose levels may provide additive anti-inflammatory effects, and therefore may improve long-term outcomes for adults with type 2 diabetes.

scholarly journals What does it mean when we ask the public if they are ‘confident’ in policing? The trust, fairness, presence model of ‘public confidence’

2019 ◽  
Vol 22 (2) ◽  
pp. 111-122 ◽  
Author(s):  
Kevin Morrell ◽  
Ben Bradford ◽  
Basit Javid
Keyword(s):  
Survey Data ◽  
Good Evidence ◽  
Fundamental Question ◽  
Police Force ◽  
Public Confidence ◽  
Single Item ◽  
The Public ◽  
West Midlands ◽  
The Relationship ◽  
Part Model

‘Confidence’ is widely taken to be a crucial measure of the relationship between citizens and public services such as policing. It is acknowledged that confidence is multifaceted and hard to measure, but often discussions are based on one ‘headline’ rating of a single item, for instance: ‘What is your level of confidence in…’. The subsequent focus for research is explaining what might drive ‘confidence’, or what it might predict. We are interested in a more fundamental question: what does it mean when we ask the public if they are ‘confident’ in policing? To answer this, we analyse extensive and detailed survey data specifically designed to measure public confidence, within the jurisdiction of a UK police force – West Midlands Police. We develop then validate a three-part model of confidence as trust, fairness and presence, and find good evidence to support this model across different waves of the survey. This extends existing literature with implications for policy.

High performance Deformable Part Model accelerator based on FPGA

2016 ◽  
Author(s):  
Qi Zhan ◽  
Min Gao ◽  
Li Jiao ◽  
Wei Cao ◽  
Xuegong Zhou ◽  
...  
Keyword(s):  
High Performance ◽  
Deformable Part Model ◽  
Part Model

Formation of Geometric Tolerance Zones for Polyhedral Objects

1997 ◽  
Author(s):  
Utpal Roy ◽  
Bing Li
Keyword(s):  
Variational Model ◽  
Tolerance Zone ◽  
Geometric Tolerance ◽  
Geometric Tolerances ◽  
Polyhedral Objects ◽  
Different Types ◽  
Tolerance Zones ◽  
Algebraic Constraints ◽  
Size Tolerance ◽  
Part Model

Abstract This paper presents a scheme for establishing geometric tolerance zones for polyhedral objects in solid modelers. The proposed scheme is based on a surface-based variational model. Variations are applied to a part model by varying each surface’s model variables. Those model variables are constrained by some algebraic relations derived from the specified geometric tolerances. For size tolerance, two types of tolerance zones are considered in order to reflect two different types of size tolerances. For any other geometric tolerance (form, orientation or positional), the resultant tolerance zone is defined by the combination of size tolerance and that particular geometric tolerance specifications. Appropriate algebraic constraints (on the model variables) are finally used to establish the tolerance zone boundaries in the surface-based variational model.

Integration of Commercial CAD/CAM System With Custom CAPP Using Orbix Middleware and CORBA Standard

2002 ◽  
Author(s):  
Fernando Rangel ◽  
Jami J. Shah
Keyword(s):  
Computer Aided Design ◽  
Numerical Control ◽  
Commercial Application ◽  
Commercial Software ◽  
Computer Aided Process Planning ◽  
Nc Code ◽  
Cad System ◽  
Computer Aided ◽  
Continuous Application ◽  
Part Model

This paper discusses the issues of integrating the Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) programs in commercial software. Integration was achieved through implementation of a computer-aided process planning (CAPP) system within the commercial software. The part model was imported into, or designed in, the commercial CAD system. Manufacturing information was then extracted from the part model by the CAPP system using commercial Application Programming Interfacing (API) methods. The CAPP system then uses the extracted information to produce a process plan consistent with the requirements of the commercial CAM module to produce Numerical Control (NC) code. The internal integration was accomplished using commercial API methods that dynamically bind the CAD, CAPP, and CAM into a single continuous application. These APIs are implemented using the Orbix middleware following the CORBA standard. A case study demonstrating the integration is presented. Strengths and weaknesses of integrating the CAD and CAM domains using APIs and middleware are discussed.

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