# Decision exercises

E = exercise; Q = exact SQL query. All operating numbers fictional. Personal responses are deliberately blank. Model answers are in a separate file and optional disclosure in the browser.

## E01 · Choose the value unit

**Decision:** Should the North Star count accounts, people, minutes or exports?

**Run:** `sql/Q01.sql`; chart `charts/Q01.svg`; data `csv/Q01_result.csv`.

**Read it:** Compare DB01 account reach with task volume and confirmation coverage.

**Counterargument:** Would one large account or repeated locale versions distort the story?

**Guardrails:** Filters use date, unlike task cards. Only whole UTC weeks fully inside the selected date range and ended before cutoff are included. Missing confirmations limit interpretation.

**Next evidence:** Confirm account identity, repeated job frequency and use-confirmation method.

**PRD sections:** 2, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E02 · Find the important handoff

**Decision:** Which stage deserves the next investigation?

**Run:** `sql/Q02.sql`; chart `charts/Q02.svg`; data `csv/Q02_result.csv`.

**Read it:** Use created tasks as the common denominator, then separate parallel review/export paths.

**Counterargument:** Could an expected rights or plan block explain the gap?

**Guardrails:** Review and export are parallel checkpoints; do not force them into a strictly ordered funnel.

**Next evidence:** Inspect real traces and task sessions; validate missing events before naming a defect.

**PRD sections:** 3, 6, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E03 · Defend activation

**Decision:** What qualifies as a first useful result?

**Run:** `sql/Q03.sql`; chart `charts/Q03.svg`; data `csv/Q03_result.csv`.

**Read it:** Count users, retain mature zero-task signups and require review/use before day seven.

**Counterargument:** Does a late review leak future information into the first week?

**Guardrails:** All mature signups, including zero-task users. Workflow filter means primary intended workflow.

**Next evidence:** Confirm whether users, accounts or invited seats are the right production denominator.

**PRD sections:** 6, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E04 · Mature repeat value

**Decision:** Which cohort merits customer-success investigation?

**Run:** `sql/Q04.sql`; chart `charts/Q04.svg`; data `csv/Q04_result.csv`.

**Read it:** Use the complete days 28–41 window, counts and cohort mix.

**Counterargument:** Are later cohorts censored or jobs naturally infrequent?

**Guardrails:** Unconditional signup return during days 28–41, not retention conditional on activation.

**Next evidence:** Interview returning and nonreturning users about need frequency and unobserved offline use.

**PRD sections:** 3, 14, 17

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E05 · Signal versus cause

**Decision:** Does activation cause later return?

**Run:** `sql/Q05.sql`; chart `charts/Q05.svg`; data `csv/Q05_result.csv`.

**Read it:** Explain the association and a future account-randomized intervention.

**Counterargument:** Could initial intent or account mix cause both?

**Guardrails:** Descriptive association; intent, account mix and confirmation coverage may explain it.

**Next evidence:** Assignment unit, sample/power, coverage and a disconfirming test.

**PRD sections:** 12, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E06 · Quality evidence first

**Decision:** Can reviewed acceptance justify expansion?

**Run:** `sql/Q06.sql`; chart `charts/Q06.svg`; data `csv/Q06_result.csv`.

**Read it:** Read review coverage, acceptance and critical-error counts together.

**Counterargument:** Who did not review, and why?

**Guardrails:** Reviewed acceptance is selected; missing review remains unknown.

**Next evidence:** Representative bilingual labels, sampling mechanism and hard-case evidence.

**PRD sections:** 12, 13, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E07 · Latency without arithmetic errors

**Decision:** Should the team reduce queue time or reviewer wait?

**Run:** `sql/Q07.sql`; chart `charts/Q07.svg`; data `csv/Q07_result.csv`.

**Read it:** Compare root ready latency with completion and Q23 human wait.

**Counterargument:** Are incomplete slow tasks excluded?

**Guardrails:** Creation to visible-ready includes wait/retry. Completer-only; inspect non-completion in Q02. Not sum of component p95.

**Next evidence:** Trace spans, timeouts and status UI observations across comparable workloads.

**PRD sections:** 11, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E08 · Recover value safely

**Decision:** Which recovery should be built first?

**Run:** `sql/Q08.sql`; chart `charts/Q08.svg`; data `csv/Q08_result.csv`.

**Read it:** Compare tasks with failures, recovered renders and recovered useful tasks.

**Counterargument:** Does render recovery actually restore use?

**Guardrails:** All failures mature at cutoff except latest-day tasks excluded by generator; recovery-to-render differs from customer value.

**Next evidence:** Failure eligibility, customer intent, observation window and debit reconciliation.

**PRD sections:** 6, 11, 17

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E09 · Cost of useful work

**Decision:** What changes cost per useful result most?

**Run:** `sql/Q09.sql`; chart `charts/Q09.svg`; data `csv/Q09_result.csv`.

**Read it:** Include failed/nonmonetized attempts and compare all service scopes.

**Counterargument:** Does low confirmation coverage inflate the denominator problem?

**Guardrails:** Includes all selected task costs incl failures; excludes period allocations, shown separately Q18. Review is vendor fraction; customer time separate.

**Next evidence:** Real invoices, provider rates, vendor/customer labor split and stable use-confirmation sampling.

**PRD sections:** 2, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E10 · Review burden

**Decision:** Does fast production save customer time?

**Run:** `sql/Q10.sql`; chart `charts/Q10.svg`; data `csv/Q10_result.csv`.

**Read it:** State preparation, review and repair separately; net estimate is not causal savings.

**Counterargument:** Is the manual baseline measured or estimated?

**Guardrails:** Manual baseline is an invented estimate; net time is not causal savings.

**Next evidence:** Matched same-task baseline, quality parity and downstream workload.

**PRD sections:** 3, 12, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E11 · Hidden cost driver

**Decision:** Which operational cost deserves attention?

**Run:** `sql/Q11.sql`; chart `charts/Q11.svg`; data `csv/Q11_result.csv`.

**Read it:** Rank dollar components, not summed heterogeneous units.

**Counterargument:** Would suppressing support tickets only hide work?

**Guardrails:** Do not add heterogeneous units; quantity and rate remain component-specific.

**Next evidence:** Support resolution quality, invoice reconciliation and utilization assumptions.

**PRD sections:** 14, 17

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E12 · Explain three meters

**Decision:** How should a failed job settle usage?

**Run:** `sql/Q12.sql`; chart `charts/Q12.svg`; data `csv/Q12_result.csv`.

**Read it:** Reconcile reserved=consumed+released+outstanding within each meter.

**Counterargument:** Could a retry create a duplicate debit?

**Guardrails:** Illustrative entitlement model, not claimed production billing. Never sum minute/credit/count units.

**Next evidence:** Actual plan/contract rules, event dedup and failure-settlement tests.

**PRD sections:** 10, 11, 13, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E13 · Reject a bad experiment readout

**Decision:** Can the apparent variant difference support rollout?

**Run:** `sql/Q13.sql`; chart `charts/Q13.svg`; data `csv/Q13_result.csv`.

**Read it:** Q13 counts mature accounts with mixed seat assignments; inspect this interference before inference.

**Counterargument:** Are team members exposed to both variants?

**Guardrails:** This lab assigns users, so team accounts can have mixed variants. This audit is not a causal comparison; fix assignment before inference.

**Next evidence:** Account-level assignment and actual exposure, preregistered success and harm criteria.

**PRD sections:** 12, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E14 · Growth worth buying

**Decision:** Which channel deserves the next experiment?

**Run:** `sql/Q14.sql`; chart `charts/Q14.svg`; data `csv/Q14_result.csv`.

**Read it:** Use mature, matched cost and activated-user cohorts; do not call this paying-account CAC.

**Counterargument:** Does channel intent or sales assistance explain activation?

**Guardrails:** Allocated synthetic spend; all users have 42-day follow-up here. Not CAC per paying account or causal channel performance.

**Next evidence:** Paying-account linkage, channel attribution, incremental acquisition test and retention.

**PRD sections:** 2, 14, 17

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E15 · Trace the evidence

**Decision:** Which records support your recommendation?

**Run:** `sql/Q15.sql`; chart `charts/Q15.svg`; data `csv/Q15_result.csv`.

**Read it:** Inspect one task per row and follow its review/use/cost IDs.

**Counterargument:** Do rows duplicate users, accounts or money?

**Guardrails:** Fictional task IDs; no customer identity or private payload.

**Next evidence:** Real event provenance and task-version integrity.

**PRD sections:** 10, 11, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E16 · Include never-starters

**Decision:** Whose absence is hidden by active-user charts?

**Run:** `sql/Q16.sql`; chart `charts/Q16.svg`; data `csv/Q16_result.csv`.

**Read it:** Retain zero-task mature users and avoid assigning a cause from absence.

**Counterargument:** Could an invitation be intended only for review?

**Guardrails:** No task does not identify the cause; no session instrumentation in this lab.

**Next evidence:** Role/intent and consented nonstarter research; session events if necessary.

**PRD sections:** 3, 6, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E17 · Commercial retention

**Decision:** Is rising MRR healthy?

**Run:** `sql/Q17.sql`; chart `charts/Q17.svg`; data `csv/Q17_result.csv`.

**Read it:** Reconcile opening+new+expansion-contraction-churn=closing; inspect GRR/NRR.

**Counterargument:** Does new revenue hide losses among existing accounts?

**Guardrails:** Full calendar months only; exclude October partial. Normalized fictional subscription MRR; not cash or actual price tiers.

**Next evidence:** Actual contracts, renewals, logo loss, refunds and accounting policy.

**PRD sections:** 2, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E18 · Full economics

**Decision:** Can the service sustain this workload?

**Run:** `sql/Q18.sql`; chart `charts/Q18.svg`; data `csv/Q18_result.csv`.

**Read it:** Preaggregate billing, task costs and period allocations separately before joining month.

**Counterargument:** Which costs and cash timing remain excluded?

**Guardrails:** Not recognized gross margin or profit; customer labor, acquisition and unmodeled overhead excluded. Task-cost month is task creation convention.

**Next evidence:** Acquisition, overhead, recognition policy and provider commitments.

**PRD sections:** 2, 14, 17

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E19 · Candidate release

**Decision:** Does a better average justify deployment?

**Run:** `sql/Q19.sql`; chart `charts/Q19.svg`; data `csv/Q19_result.csv`.

**Read it:** Pair heldout source cases and inspect critical errors, latency and cost by slice.

**Counterargument:** Does a critical slice get worse?

**Guardrails:** Fictional paired cases, not actual model output; no real release evidence.

**Next evidence:** Rights-cleared real media, independent bilingual labels and source-isolated split.

**PRD sections:** 12, 13, 17

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E20 · Trust an automated judge?

**Decision:** Should automated review replace bilingual checks?

**Run:** `sql/Q20.sql`; chart `charts/Q20.svg`; data `csv/Q20_result.csv`.

**Read it:** Compute failure-detection recall and false alarms; inspect critical misses.

**Counterargument:** How many important failures did the judge miss?

**Guardrails:** Synthetic labels; compute failure recall, inspect slices and critical misses before using a live blocking judge.

**Next evidence:** Real adjudicated labels, agreement slices and operational false-positive costs.

**PRD sections:** 12, 13

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E21 · Choose feasible scope

**Decision:** Which opportunity fits actual capacity?

**Run:** `sql/Q21.sql`; chart `charts/Q21.svg`; data `csv/Q21_result.csv`.

**Read it:** Account for dependencies and separate engineering, design and review weeks.

**Counterargument:** What if reviewer capacity, not engineering, is binding?

**Guardrails:** Proposed estimates, no effect size or confidence probability; high reach is not a forecast.

**Next evidence:** Actual capacity, range estimates, demand evidence and opportunity cost.

**PRD sections:** 1, 4, 16

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E22 · Release versus readiness

**Decision:** Which missing gate prevents pilot?

**Run:** `sql/Q22.sql`; chart `charts/Q22.svg`; data `csv/Q22_result.csv`.

**Read it:** All gate states are unverified; name the evidence and accountable role.

**Counterargument:** Does a well-written test count as a passed test?

**Guardrails:** All proposed gates unverified; no actual product release performed.

**Next evidence:** Actual test results, support readiness, approval and rollback drill.

**PRD sections:** 1, 12, 17

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E23 · One elapsed-time story

**Decision:** Where is the customer's real wait?

**Run:** `sql/Q23.sql`; chart `charts/Q23.svg`; data `csv/Q23_result.csv`.

**Read it:** Distinguish ready-to-review wait, active work and total time to use.

**Counterargument:** Are unconfirmed long tasks censored?

**Guardrails:** Different completed populations in each duration; missing review/use may censor long waits.

**Next evidence:** Incomplete durations, reviewer staffing and end-to-end observation.

**PRD sections:** 6, 11, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**

## E24 · Explain recorded paths

**Decision:** Where does the last recorded step occur?

**Run:** `sql/Q24.sql`; chart `charts/Q24.svg`; data `csv/Q24_result.csv`.

**Read it:** Use timestamp-ordered edges and conservation; review/export can swap order.

**Counterargument:** Are skipped events instrumentation gaps or true behavior?

**Guardrails:** Ordered by actual timestamps; review/export can occur in either order. Last recorded is not proven abandonment.

**Next evidence:** Observed task traces and missing event tests.

**PRD sections:** 6, 10, 14

**Spoken task:** State one takeaway, one caveat and one action in 30 seconds. Then stop.

**Your answer:**


**Your score and elapsed time:**