Objective and professional context
The fictional source has four observed sessions and three completed orders. Two orders belong to session S1 and one belongs to S2; S3 and S4 have no purchase. Counting orders therefore differs from counting purchasing sessions. A conversion definition must name the event, eligible population and observation window before a percentage is useful. The identifiers are synthetic and do not describe real customers.
Your practical assignment
Calculate session conversion and orders per session. Add a fourth order to S1 in a working copy and predict which measure should change. Explain how a join at the wrong grain could inflate the result.
Worked solution and interpretation
Two of four sessions purchased, so session conversion is 50%. Three orders over four sessions is .75 orders/session. A fourth order in S1 changes orders/session to 1 but leaves purchasing-session conversion at 50%. Those definitions answer different questions.
Verification, mistakes and limits
Use COUNT(DISTINCT session_id) over eligible completed orders for the numerator and the full eligible session table for the denominator. Preserve non-purchasing sessions and validate source keys. A percentage from this tiny extract is not customer retention, lifetime value, a causal marketing effect or a real customer persona.
Continue with evidence
Keep the unchanged data, your implementation and a changed-input result with a short note explaining what you can and cannot conclude. These free companions do not change saved course progress. The published course catalogue shows deeper assignments available under your current permissions. Keep your conclusions proportional to the evidence you have inspected.
Authoritative reference
Official technical method reference; it does not validate fictional outcomes or your own software environment.
Try the activity before reading its reference. Keep your sources, commands and assumptions with your work. Companion activities are unsaved self-practice and do not award a certificate or change lesson progress.