The queue has shrunk. Has the work?
We closed 80 cases this month, so the backlog must have fallen by 80.
The case
A fictional team begins with 200 open cases. During the month, 70 new cases arrive, 80 are closed, and 20 previously closed cases reopen. All counts refer to the same boundary and period; reopened cases are additional to new arrivals.
Try it before reading on
Calculate the closing backlog. Then write one claim the calculation supports and one causal claim it cannot support.
Use paper or your own notes. Keep the first answer as well as any revision.
Compare your reasoning
The closing backlog is 200 + 70 − 80 + 20 = 210 cases. The stock increased by ten despite eighty closures. The calculation checks the supplied accounting identity. It cannot establish why cases reopened, whether closures were appropriate, or which intervention would improve resolution. Investigate the closure and reopening rules before treating gross activity as capacity.
When could the claim be defensible?
An eighty-case reduction would follow if there were no arrivals or reopenings and no other changes to the boundary. That is a different set of assumptions, not an arithmetic alternative.
Change the conditions
Twenty cases are transferred to another team and removed from this backlog. Calculate the local total and state what is still unknown.
Compare the changed case
The local backlog is now 190. The receiving team's burden and the people's total wait remain unknown. A smaller local stock can coexist with unchanged or worse end-to-end performance.
Follow the specific connection
System Dynamics: build, calculate and challenge a queue model
An original discrete-time stock-flow rehearsal with a deliberately simple boundary. It is not a prediction of a real service and does not validate a model merely because it runs.
Evaluation and reflexivity: test the claim you are tempted to make
A basic mixed-evidence evaluation rehearsal. It is not a complete impact evaluation, statistical inference course or assessment of real practitioner behaviour.
Source routes and reading limits
The methodological route below uses the existing practice pack's checked resource descriptions. This release does not claim fresh reading of the external works.
MIT: System Dynamics Self Study, assignments and solutions
Start with the early assignments and their paired solutions. Predict behaviour, calculate it, then compare. Do not confuse this course with MIT courses that publish assignments without solutions.
Existing check: Assignment/solution pairs on the MIT page inspected. Historic software instructions may need adaptation; the whole course was not executed.
UK Government: introductory systems thinking toolkit
Select the named tool, try the associated template and compare with the example. Use the pack's explicit checks where the toolkit provides no answer key.
Existing check: HTML toolkit inspected, including mapping, stock-flow, theory of change and evaluation sections. Its examples are not automatic validation of a learner's model.
Deming Institute: PDSA cycle
Write a prediction before a change and compare observation with it. The service and evaluation cases here give a small exercise and answers.
Existing check: The Institute's account of prediction, study and theory revision inspected. It distinguishes PDSA from a simple implementation check.
Wenger-Trayner: systems convening, free book and resources
Use the cases to examine legitimacy, boundaries, agency and learning partnerships. The original case here provides the checkable rehearsal.
Existing check: Authors' page, free PDF route and paperback links inspected. It is a related social-learning resource, not identical to every method grouped in the bridge exercise.
Take one revision away
Write the claim you can now support, the assumption you changed, and the observation or decision still needed. Do not turn the worked comparison into a compulsory answer where the question admits alternatives.
Choose another claim · Print all task sheets · Download the cases and route record