Study Data Collection: Calendar Triggered Events

Most studies have data-collection schedules built around events that happen to the participant. For example, a participant completes baseline and then has monthly follow-ups for three months. If two participants enroll a week apart, their follow-ups generally stay a week apart throughout the study. Each participant's study events anchor their own collection schedule.

But that's not the only way to build a schedule. Sometimes the calendar itself can be the anchor.

We recently encountered this with a study that included monthly online data collection. Participants were asked to complete forms during the first week of every month. The collection window opened on the 1st and closed after the 7th.

Someone who started on the 1st had the full seven days to complete the forms. If someone didn't start until the 5th, only two days remained. Once the window closed, that month's collection event was over.

The reminders worked around the same calendar schedule. Everyone received a notification when the window opened on the 1st. Participants who hadn't started or completed their forms could then receive additional reminders, such as a reminder each day. The reminders followed the participant's progress, but the collection window didn't move.

This also changes what happens when someone enters the study. A participant enrolled in the middle of the month wouldn't necessarily begin monthly data collection immediately. Their first collection could wait until the window opened on the 1st of the following month. Once enrolled, all participants would then complete their monthly questionnaires during the same calendar-defined windows.

A Few Ways This Can Work

The collection window itself can be used in different ways.

• Completely online data collection. Participants complete questionnaires or other activities remotely during the collection window.
• Participant-managed activities. Participants are responsible for completing an activity, measurement, or other study task sometime during the window.
• Scheduled study visits. Staff and participants coordinate a visit that can occur at any point during the window. The actual visit date can then determine how much time remains for related activities or follow-up forms that also need to be completed within that window.

Why It Matters

There can be both empirical and practical reasons for keeping participants on the same calendar.

Sometimes the timing matters to what you're trying to measure. Suppose you're interested in people's reactions to current events. Collecting everyone's responses during roughly the same period helps keep participants aligned with a similar news environment. Or perhaps you're studying financial stress, where bills, rent, pay cycles, and other pressures may have a monthly cadence. In those cases, collecting data during the same part of each month may be more meaningful than collecting it a fixed number of days after each participant enrolled.

More generally, if the phenomenon you're studying has a calendar-based rhythm, there may be good reason for the data collection to follow that rhythm too.

Other reasons can be purely practical. A study involving group interventions, for example, may be easier to run if participants move through activities together rather than on dozens of individual schedules. The same can be true for staffing. Keeping participants within common collection windows can make it easier to schedule staff, coordinate visits, deliver an intervention, or manage follow-up.

Another data-collection approach to add to your toolkit.