* A likelihood-based two-part marginal model for longitudinal semicontinuous data.
- Two-part models are an attractive approach for analysing longitudinal semicontinuous data consisting of a mixture of true zeros and continuously distributed positive values. When the population-averaged (marginal) covariate effects are of interest, two-part models that provide straightforward interpretation of the marginal effects are desirable. Presently, the only available approaches for fitting two-part marginal models to longitudinal semicontinuous data are computationally difficult to implement. Therefore, there exists a need to develop two-part marginal models that can be easily implemented in practice. We propose a fully likelihood-based two-part marginal model that satisfies this need by using the bridge distribution for the random effect in the binary part of an underlying two-part mixed model; and its maximum likelihood estimation can be routinely implemented via standard statistical software such as the SAS NLMIXED procedure. We illustrate the usage of this new model by investigating the marginal effects of pre-specified genetic markers on physical functioning, as measured by the Health Assessment Questionnaire, in a cohort of psoriatic arthritis patients from the University of Toronto Psoriatic Arthritis Clinic. An added benefit of our proposed marginal model when compared to a two-part mixed model is the robustness in regression parameter estimation when departure from the true random effects structure occurs. This is demonstrated through simulation.
Overview of verb demonstrate
The verb demonstrate has 4 senses (first 4 from tagged texts)
1. (24) show, demo, exhibit, present, demonstrate -- (give an exhibition of to an interested
audience; "She shows her dogs frequently"; "We will demo the new software in Washington")
2. (22) prove, demonstrate, establish, show, shew -- (establish the validity of something, as by an
example, explanation or experiment; "The experiment demonstrated the instability of the compound";
"The mathematician showed the validity of the conjecture")
3. (2) attest, certify, manifest, demonstrate, evidence -- (provide evidence for; stand as proof of;
show by one's behavior, attitude, or external attributes; "His high fever attested to his illness";
"The buildings in Rome manifest a high level of architectural sophistication"; "This decision
demonstrates his sense of fairness")
4. (1) demonstrate, march -- (march in protest; take part in a demonstration; "Thousands
demonstrated against globalization during the meeting of the most powerful economic nations in
Seattle")
Overview of adj demonstrated
The adj demonstrated has 1 sense (first 1 from tagged texts)
1. (1) demonstrated -- (having been demonstrated or verified beyond doubt)
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