To create a framework for the conversation, we wanted to introduce and build consensus around the following concepts. Please provide your feedback on these concepts/rules.
1. Evaluation/Target cohort vs comparator/outcome cohort: An analyst will be able to select one or more cohorts for characterization. One of the selected cohorts will be the comparator cohort, and all other cohorts will be the evaluation cohort (s). Evaluation cohorts will be compared to comparator cohorts. Differences between the evaluation and comparator cohorts will be calculated using measures such as standard difference.
2. Index period or Day 0: Cohort start date will be the index period or Day 0.
3. Cohort period: Interval period as any time interval between a subject_id’s cohort-start-date and cohort-end-date, including both dates will be the cohort period for that subject_id.
4. Baseline period: Interval period as any time interval prior to (not including) cohort start date, and going as back as the beginning of the subject_id’s first observation_period_start_date, and in the persons observation period.
5. No overlaps: As a rule, an analysis will have to either belong to the cohort-period, or the baseline period – there will be no overlapping periods that cross over from baseline period to cohort period.
6. Time series However, analysis maybe divided into discrete intervals of time for use in temporal/time series analysis. Time periods may be divided based on a) Relative time period (every 1 day, 7 days, 30 days, 90 days, 180 days, 365 days), or b) calendar period - (every calendar week, calendar year-month, calendar year-quarter, calendar year), or both.