How a definition is adopted
Kestrel Fitness 3 in collision check 1 comparison overdue
One register of what every figure in the Kestrel monthly pack means: the calculation, the source, the owner, the client approver and the date each definition takes effect. Kept by Arjun Mehta, analytics lead at Northfold Analytics, with Sofia Reyes, senior analyst, and read by Grace Whitfield, head of membership data at Kestrel Fitness. Register as of October 1, 2026.
- Proposed
- Collision check
- Client review
- Approved
- Effective
A definition enters as Proposed with an owner, a calculation, a source field and a period basis. In Collision check Northfold tests it against every existing measure that shares its name, its population or its period basis. Grace Whitfield approves it in Client review, Arjun Mehta then sets the effective date, and an approved definition is never applied to packs that have already been released. Rejected and Superseded definitions stay in the register with their reason, so the same debate is not repeated. The position marked above is Visits per active member, which is in Collision check today.
Effective register
Seven Kestrel Fitness definitions are in force or approved with a start date: five effective in the pack and two approved. The live register below lists each with its calculation, source, owner, approver and effective date. A row dated after today, such as Cancellation rate (Oct 5) or Membership revenue per active member (Oct 26), is approved but not yet in a released pack.
Collision rules
A collision is two figures that carry the same name or the same idea but are calculated differently. Four rules apply before any definition reaches Grace:
- One name, one calculation. A figure that counts differently gets its own name.
- One period basis. The register uses four-week periods, so a calendar month figure is restated before it is adopted.
- No overlap inside a ratio. A numerator and a denominator must not count the same members twice.
- A comparison that runs past its due date goes to Arjun Mehta, and the definition stays in Collision check until it is finished.
Recent changes
Kestrel Fitness definitions that moved since August, newest first. Packs affected counts the packs a change touches, and an approved change is not restated into earlier packs.
| Date | Definition | Status | What changed | Packs affected |
|---|---|---|---|---|
| Oct 26, 2026 | Membership revenue per active member | Approved | Approved by Grace Whitfield on Sep 30. Starts with the pack for the period beginning Oct 26; earlier packs are not restated. | 3 |
| Oct 5, 2026 | Cancellation rate | Approved | Takes effect with the October pack and replaces Monthly churn rate, which is Superseded with its history kept. | 4 |
| Sep 30, 2026 | Average membership length | Client review | Grace Whitfield asked to exclude cancellations inside the 14 day cooling off window. Sofia Reyes is rerunning September with and without them. | 1 |
| Sep 29, 2026 | Visits per active member | Collision check | Restatement in four-week periods requested by Arjun Mehta. | 2 |
| Sep 21, 2026 | Inactive member share | Rejected | Grace Whitfield preferred one visit measure, and Visits per active member already covers member activity. | 0 |
| Sep 7, 2026 | Peak hour check-ins | Effective | In force for staffing rotas. Guest passes are included because they use the same turnstile event. | 2 |
| Aug 24, 2026 | Reactivated members | Effective | The 90 day gap that keeps short pauses out of joiner figures was agreed with Grace Whitfield on Aug 20. | 1 |
| Aug 10, 2026 | New joiners | Effective | Returning members are counted in Reactivated members, so the two figures never overlap. | 3 |
Definition card
Every entry in the register carries the same card. The example is Cancellation rate, which Grace Whitfield approved and which first appears in the October pack.
- Status
- Approved, effective Oct 5, 2026
- Definition
- Share of members active at the start of the period who cancelled during it.
- Calculation
- Cancellations in the period divided by active members at period start.
- Source
- Finance export, field cancellation.date
- Period basis and unit
- Four-week period, percent
- Definition owner
- Arjun Mehta, Northfold Analytics
- Client approver
- Grace Whitfield, Kestrel Fitness
- Replaces
- Monthly churn rate, kept as history for packs before Oct 5, 2026
- Packs affected
- 4
- Collision note
- Takes effect with the October pack and replaces Monthly churn rate.
Review cadence
The register is reviewed before every pack is assembled. Anything past its due date is raised with Arjun Mehta the same day.
Register review, every pack release
- List approved definitions with their effective dates before the pack is assembled (Arjun Mehta)done
- Record the Oct 26 start of Membership revenue per active member, approved by Grace Whitfield on Sep 30done
- Record the rejection of Inactive member share on Sep 21 with its reasondone
- Resubmit Visits per active member in four-week periods and name the measure it replaces (Tomas Ferreira, requested Sep 29)open
- Finish the Class fill rate comparison once the timetable export covers all fourteen clubs (Tomas Ferreira, due Sep 26, overdue)open
- Get Grace Whitfield's answer on corporate trial passes for Trial conversion rate (waiting since Sep 25)open
- Rerun September Average membership length with and without cooling off cancellations (Sofia Reyes)open
- Tell Grace Whitfield that Cancellation rate takes effect on Oct 5 (Arjun Mehta)open
| Register in use, Q3 2026 (sample figures) | Result |
|---|---|
| Figures disputed by Kestrel | 3 |
| Time to explain a discrepancy | Same day, from the register entry |
| Packs affected by approved changes | 7 (Cancellation rate 4, Membership revenue per active member 3) |
| Onboarding time for a new analyst | Not measured yet |
Who keeps the register
- Arjun MehtaAnalytics lead, Northfold Analytics, definition owner and effective dates
- Sofia ReyesSenior analyst, Northfold Analytics, collision checks and proposals
- Grace WhitfieldHead of membership data, Kestrel Fitness, client approver