Non-decreasing threshold variances in mixed generalized ordered response models: A negative correlations approach to variance reduction

This study highlights a potential limitation of these models, as applied in most empirical research, that the variances of the random thresholds are implicitly assumed to be in a non-decreasing order. This restriction is unnecessary and can lead to difficulty in estimation of random parameters in higher order thresholds. In this study, we investigate the use of negative correlations between random parameters as a variance reduction technique to relax the property of non-decreasing variances of thresholds in MGOR models. To this end, a simulation-based approach was used (where multiple datasets were simulated assuming a known negative correlation structure between the true parameters), and two models were estimated on each dataset – one allowing correlations between random parameters and the other not allowing such correlations. Allowing negative correlations helped relax the non-decreasing variance property of MGOR models. However, maximum simulated likelihood estimation of parameters on data with correlations occasionally encountered model convergence and parameter identification issues. Comparison of the models that did converge suggests that ignoring correlations leads to an estimation of fewer random parameters in the higher order thresholds and results in bias and/or loss of precision for a few parameter estimates. However, ignoring correlations leads to an adjustment of other parameter estimates such that overall likelihood values, predicted percentage shares, and...
Source: Analytic Methods in Accident Research - Category: Accident Prevention Source Type: research

Related Links:

Publication date: Available online 18 August 2019Source: NeuroImage: ClinicalAuthor(s): Eva Matt, Florian Ph.S. Fischmeister, Thomas Foki, Roland BeisteinerAbstractApraxia is a deficit in central motor planning impairing praxis functions such as gesture production or tool use that affects a substantial number of patients with advanced Parkinson's disease. We investigated the functional connectivity of the praxis network in patients in early stages of Parkinson's disease having an increased risk for apraxia and evaluated the influence of dopaminergic therapy on praxis abilities and related networks.13 patients with mild to ...
Source: NeuroImage: Clinical - Category: Radiology Source Type: research
Manzi is the chair, Department of Medicine at Allegheny Health Network.
Source: bizjournals.com Health Care:Pharmaceuticals headlines - Category: Pharmaceuticals Authors: Source Type: news
What is the prevalence of anxiety and depressive symptoms in IBS patients, and how do rates compare with healthy controls?Alimentary Pharmacology &Therapeutics
Source: Medscape Today Headlines - Category: Consumer Health News Tags: Gastroenterology Journal Article Source Type: news
What strategies do adults with long-term mobility impairment, such as serious difficulty walking or climbing stairs, use to maintain activities of daily living in the face of age-related changes?The Gerontologist
Source: Medscape Today Headlines - Category: Consumer Health News Tags: Internal Medicine Journal Article Source Type: news
The authors challenge the epidemiological, clinical, pathophysiological, and therapeutic basis for classifying heart failure solely according to LVEF.European Heart Journal
Source: Medscape Today Headlines - Category: Consumer Health News Tags: Cardiology Journal Article Source Type: news
A new study suggests that leukocyte telomere length may be useful for predicting AF recurrence after ablation.Journal of Cardiovascular Electrophysiology
Source: Medscape Today Headlines - Category: Consumer Health News Tags: Cardiology Journal Article Source Type: news
Could decreased overnight melatonin levels be useful as a predictive marker for next day migraine in children and adolescents?Headache
Source: Medscape Today Headlines - Category: Consumer Health News Tags: Neurology & Neurosurgery Journal Article Source Type: news
This case of a patient colonized with Candida auris after extended hospitalization in Kenya underscores how health care exposure outside the US is a risk factor for emerging drug-resistant infections.Morbidity &Mortality Weekly Report
Source: Medscape Today Headlines - Category: Consumer Health News Tags: Public Health & Prevention Journal Article Source Type: news
HIGH blood pressure is a common condition that can lead to serious and even life-threatening health complications if left untreated. But one of the best ways to avoid these complications and keep blood pressure under control is by making healthy food swaps. So what ’s the best food to eat for breakfast?
Source: Daily Express - Health - Category: Consumer Health News Source Type: news
The Saskatchewan Wildlife Federation is calling for a ban on hunting baits and for mandatory chronic wasting disease testing on any deer, elk or moose killed by hunters.
Source: CBC | Health - Category: Consumer Health News Source Type: news
More News: Accident Prevention | Accidents | Study