Intensive longitudinal data (ILD) are data with many measurements over time. A limit of 40 observations is often used a threshold, but the characteristics of the data are much more important than the number of observations.
Time-Varying Effect Model (TVEM)
Methodology Center research on ILD focuses on the time-varying effect model (TVEM), which lets researchers see changes in relationships between variables without making assumptions about the nature of those relationships.
Thanks to smartphones and other technological advances, ILD are becoming more and more common. This rich data can offer scientists the ability to answer many interesting questions that were previously unanswerable.
Introductory Example: The Dynamics of Quitting Smoking
TVEM makes it possible for scientists to observe change over time in the factors that influence an outcome. For example, attempts to quit smoking are influenced by a broad range of factors, including mood, belief in one's ability to quit, and stress level. Using TVEM, we can model the changes in these relationships. This allows us to determine when and under what circumstances an individual might need additional support in order to succeed.