Mobile Research Diary — Smartphone-Based Diary Data Collection

Experience Sampling (ESM) typically uses brief, standardised questionnaire items delivered at random or semi-random intervals throughout the day to capture momentary states. A Mobile Research Diary may use similar technology but typically involves longer, more reflective entries — often end-of-day — that allow richer narrative responses. The two methods overlap and are sometimes combined: quantitative momentary ratings (ESM) plus qualitative daily narratives (diary).

Purpose-built diary and ESM platforms such as m-PATH, Qualtrics (with scheduled distributions), PIEL Survey, or ExperienceSampler are commonly used in research. The choice depends on budget, entry format needs, and institutional data-security requirements. Commercial messaging apps (WhatsApp, email) are sometimes used for low-resource projects but offer weaker data-management features.

For qualitative analysis, 10–20 participants providing daily entries over 1–4 weeks typically yields rich, analysable data. For quantitative multilevel modelling, 50 or more participants are usually recommended to have sufficient power at the between-person level. The key is that each participant provides enough time-points (at least 5–10 entries) to estimate within-person variation reliably.

Some missing data are expected; a common benchmark is to exclude participants who complete fewer than 50–70% of expected entries. Multilevel models can handle moderate missingness assuming entries are missing at random. Document and report your missingness threshold and the actual compliance rate, as these affect the credibility of your findings.

Yes, and it can be preferable to face-to-face methods for sensitive topics because participants record privately on their own device without an interviewer present. However, greater care is needed around data encryption, anonymisation of time-stamps and locations, secure server storage, and clear participant guidance on what to do if an entry triggers distress.