C.28.CM:4.2 - Turn the story into variables with subject meaning

Choose quantities or distinctions that can vary across the relevant cases or times. Give each a meaning, possible values and observation time. A particular late delivery is a case; its lateness is a value of a selected variable. Whether a variable is binary, ordinal or continuous depends on the question and measurement.

Separate the subject quantity from its registration when that difference matters. For example, distinguish an identifier present in the submitted report, a log entry reporting its absence, and inclusion of that report in an incident sample. Recover how the observation is produced through C.16 when needed. A copied ticket is another report of the same event, not another occurrence of it.

Retain enough distinctions for the proposed contrast. Combining two stages is unsafe when the action can change one while leaving the other unchanged. Conversely, a single “ready for dispatch” variable may suffice until readiness failures require different responses.