| Full text | |
| Author(s): |
Garay, Aldo M.
;
Castro, Luis M.
;
Leskow, Jacek
;
Lachos, Victor H.
Total Authors: 4
|
| Document type: | Journal article |
| Source: | STATISTICAL METHODS IN MEDICAL RESEARCH; v. 26, n. 2, p. 25-pg., 2017-04-01. |
| Abstract | |
In acquired immunodeficiency syndrome (AIDS) studies it is quite common to observe viral load measurements collected irregularly over time. Moreover, these measurements can be subjected to some upper and/or lower detection limits depending on the quantification assays. A complication arises when these continuous repeated measures have a heavy-tailed behavior. For such data structures, we propose a robust structure for a censored linear model based on the multivariate Student's t-distribution. To compensate for the autocorrelation existing among irregularly observed measures, a damped exponential correlation structure is employed. An efficient expectation maximization type algorithm is developed for computing the maximum likelihood estimates, obtaining as a by-product the standard errors of the fixed effects and the log-likelihood function. The proposed algorithm uses closed-form expressions at the E-step that rely on formulas for the mean and variance of a truncated multivariate Student's t-distribution. The methodology is illustrated through an application to an Human Immunodeficiency Virus-AIDS (HIV-AIDS) study and several simulation studies. (AU) | |
| FAPESP's process: | 13/21468-0 - Measurement error-in-variables models for censored data using scale mixtures of skew-normal distributions |
| Grantee: | Aldo William Medina Garay |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |
| FAPESP's process: | 14/02938-9 - Estimation and Diagnostics for Censored Mixed effects Models using Scale Mixtures of Skew-Normal Distributions. |
| Grantee: | Víctor Hugo Lachos Dávila |
| Support Opportunities: | Regular Research Grants |
| FAPESP's process: | 14/11831-3 - Métodos Computacionais Modernos em Modelagem estocástica |
| Grantee: | Víctor Hugo Lachos Dávila |
| Support Opportunities: | Research Grants - Visiting Researcher Grant - International |
| FAPESP's process: | 12/19445-0 - FLEXIBLE MODELING OF COMPLEX LONGITUDINAL DATA USING SKEW-ELLIPTICAL DISTRIBUTIONS |
| Grantee: | Víctor Hugo Lachos Dávila |
| Support Opportunities: | Research Grants - Visiting Researcher Grant - International |