What is a Longitudinal Study?

At a Glance

Longitudinal studies collect data on multiple occasions from the same contributors over a defined period of time.


Longitudinal studies (often called "diary studies") can provide valuable insight into how contributors over time (often 1–2 weeks) behave and interact in their everyday lives with their surroundings, products and services, or brands. 

Researchers will structure the longitudinal study using the “Diary Study Sandwich Method,” which revolves around multiple research touchpoints. These touchpoints often involve, but are not limited to...

  • An initial interview to better understand the participants and their needs relative to the topic in question.
  • Remote ummoderated touchpoints (3–4 in total) that gather contributor in-context behavior as captured through mobile or desktop devices. For instance, contributors purchasing kitchen items in store might...
    • Chart their shopping journey over a week by first capturing their planning process.
    • Then document their in-store shopping experience.
    • Finally describe how they organize their kitchen once items are purchased. 
  • A final interview to review the touchpoints and probe deeper into topics of interest captured during the overall study.

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