Longitudinal Data Analysis

Definitions

Data Structure

• 'long' format: one row. for each time point by subject combination
• 'wide' format: one row per subject

Properties

• repeated observations are usually correlated
• robust to missing data and irregularly spaced measurement occasions (only if Mixed effect modeling was used)

Modeling strategies

Traditional methods

• ANCOVA (adjusting for baseline differences)
• Repeated-measures ANOVA (univariate approach)
• MANOVA (multivariate approach)

Newer methods

• Generalized Estimating Equations (GEE) Models
• Structural Equations Models
  • used for modeling the relationships among observed and latent variables based on a set of specified structural equations
  • a multivariate statistical method that combines aspects of factor analysis and multiple regression analysis
• Transition Models
• Mixed-effects Models