The uniform data collection, consistent definitions, time synchronization process and large sample size in this population-based cohort study were intended to minimize these potential sources of bias.
It is however of note that there has been effort to systematically collect in standardized fashions, core data from patients with CKD and or commencing dialysis in this setting, which limits the potentially effects of missing data, and make data collection consistent across years.
However, despite these limitations, we believe that our study is valid, given the use of uniform data collection and consistent definitions based on the Utstein guidelines [ 24, 25] and the relatively large sample size as an observational study of pediatric OHCA in a nationwide population-based setting.
This staged approach to data collection is consistent with the funnel analogy described by Bogdan and Biklen [ 34].
Data collection was consistent, where possible, with the previous years' landline RDD phone surveys and between frames.
This approach was based on both interpretive phenomenology and data collection approaches consistent with enabling the active participation of children and young people.
Despite the small number of participants in the study the amount and type of data collection was consistent with qualitative studies of this type.
Of these students, 45.3 % (n = 1424) completed questionnaires at all time points, and 30.5 % (n = 959) completed questionnaires in at least two waves of data collection, generally consistent with longitudinal studies examining suicidality [ 19].
Although some EMA researchers suggest prompting diary completion at random intervals each day (e.g. [ 4]), recent work suggests that data collection at consistent times each day is equally valid [ 35], and may increase the convenience of, and compliance to, the data collection procedure for participants.
It would be a methodological advance if thermal cameras could measure air temperatures too, as it would make mobile data collection more efficient, consistent, and precise.
The main results showed that all 19 universities were currently collecting concussion data with athletes before, during, and after a concussion, with acute data collection being more consistent with the recommended symptoms checklist.
