A total can mix people or items at very different stages. New readers and long-time readers, for example, may have had different opportunities to return or complete a task.
A cohort groups observations by a shared starting condition, such as the period in which an activity began. Compare like stages and keep the inclusion rules explicit. The grouping should fit the question rather than be chosen because it produces a striking pattern.
Check the size of each group and the time available to observe it. A recent cohort may have an incomplete window. Naming the shared start makes the comparison easier to assess while keeping those differences visible.
Try the idea in context.
Consider two reading guides tested by readers with different prior experience. The comparison needs context about that difference as well as their completion times.
A thought for the next read.
Look for the comparison behind the visual impression. The baseline, time window, and group definition can change what a pattern seems to mean.
- Define the shared starting condition.
- Compare equivalent stages.
- Check group size and available observation time.
Follow a related question
Describe a scene at two scales.
Changing the scale of a questionDescribe the shared expectations.
Small interfaces with a long lifeKeep learning
Related background to continue exploring this subject.
NIST: statistical engineering NIST: the International System of Units
