Assignments
- Day 1:
- Reading: Overview chapter from van Belle, Fisher, Heagerty
and Lumley (2004)
- LDA Chapter --- chapter that
overviews longitudinal data analysis methods
- Day 2:
- Reading: (optional) DHLZ Chapters 3 and 4; or FLW Chapters 2 and 3
- Reading: (optional) Edwards (2000) article; Littell (2000) article -- both located in "Handouts" section of web page.
- Analysis: MACS CD4 and viral load data
- MACS-cd4-vload0.raw --- Multicenter AIDS Cohort Data
- MACS-cd4-vload0.txt --- documentation
- MACS-cd4-vload0-999.raw --- Multicenter AIDS Cohort Data with -999 rather than NA for missing values
- [1] Input the data and summarize the distribution of baseline viral load.
- [2] Summarize the distribution of CD4 in years 1, 2, 3, and 4.
- [3] Summarize the mean CD4 (and standard deviation) in years 1, 2, 3, and 4 separately
for groups based on baseline viral load (see Table 18.1 of VFHL).
- [4] Plot individual series of longitudinal observations for a selection of subjects.
- [5] Characterize the correlation among CD4 measurements.
- [6] Compute a slope over time for each subject and summarize these slopes.
- [7] Plot slopes versus the log baseline viral load. Is there an apparent association
between the baseline viral load and the subsequent rate of decline? (see
Figure 18.5 in VFHL).
- [8] Use linear mixed models to evaluate whether the level of CD4 and/or the rate of
decline in CD4 is associated with the baseline viral load.
- [9] Provide an interpretation for the estimates of the variance for the random effects
(random intercepts, random slopes).
- [10] Use generalized estimating equations (GEE) to evaluate whether the level of CD4
and/or the rate of decline in CD4 is associated with the baseline viral load.
- Comments on Exercise:
- Day 3
- Reading: Hanley et al. (2003) AJE paper -----
Hanley (2003)
- Reading: Hu et al. (1998) AJE paper -----
Hu (1998)
- Analysis: Infection and vitamin A
- xerop.raw --- Xeropthalmia data
- xerop.txt --- documentation
- [1] Input the data and summarize the prevalence of respiratory infection as a function of age (using descriptive methods).
- [2] Characterize the within-subject correlation of the binary infection outcomes.
- [3] Controlling for age and season, use GEE to evaluate whether there is an association between xeropthalmia (vitamin A deficiency) and risk of respiratory infection.
- [4] Controlling for age and season, use a GLMM to evaluate whether there is an association between xeropthalmia (vitamin A deficiency) and risk of respiratory infection.
- Comments on Exercise:
- Day 4:
- Reading: (optional) Missing Data: chpt 13 of DHLZ, and/or chpt 14 of FLW
- Optional article:
Raghunathan (2004)
--- Annual Review of Public Health.
Discusses methods for general types of missing data (not just
drop-out).
- Optional article:
Hogan et al. (2004)
--- Statistics in Medicine.
Tutorial article regarding drop-outs in longitudinal studies.
- Optional article:
Houck et al. (2004)
--- Psychiatry Research.
Compares different methods.
- Optional article:
Wood et al. (2004)
--- International Journal of Epidemiology.
Compares different methods.
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