REDCap - Longitudinal Data Collection

By default, new projects will use the 'classic' data collection format, which is the best option if all data collection instruments will only need to be used once for each record in the project. If some instruments need to be utilized repeatedly a specific *finite* number of times (e.g., using an instrument named 'Visit Data' over ten visits for the same subject), then 'longitudinal' data collection will likely be best. Additionally, the longitudinal format also allows one to utilize the scheduling module, if needed.

NOTE: If you are looking to repeat instruments *without limit* (i.e., ad hoc repetition), then you should instead use the 'repeating instruments and events' option seen on the Enable Optional Modules step on the Project Setup page. With longitudinal data collection, you must up front create all the events you wish to utilize for reusing an instrument more than once. However, with 'repeating instruments and events', you can repeat them a different number of times *without limit for each record*.