Longitudinal Data Analysis involves analyzing data which spans over a set period of time. For example, each participant may be asked to answer a questionnaire every few months, and the change in their response is modeled for trends.

Many new methods have been developed to deal with longitudinal data. These methods differ from more common methods used to analyze single time point data, and thus should not be analyzed similarly.

When analyzing longitudinal data, correlation between each two adjacent time points must be taken into account, as well as changes within each subject and between all subjects.

Mixed models, having both fixed and random effects are great for analyzing this type of data.

Contact Statistical Consulting Network for help with your Longitudinal Data Analysis