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Thinking in Diagrams

Chapter 7: Stocks Inside Feedback

Drafted for Aryeh's edit.

For chapter 7: Stocks Inside Feedback

Timing

Section titled “Timing”
  • Reading the chapter: about 10 minutes, its 1,564 words of prose at 150 words a minute. Not counted in those minutes: 3 figures, 1 pair, 2 understanding checks, the reading exercise and the exercises.
  • A session: 50 minutes, the exercises set for it. (estimate)
  • Afterwards: 100 minutes, the exercises set for then. (estimate)

Common misreadings

Section titled “Common misreadings”
  • Material vanishing between stages. In the bad diagram, the library’s books leave the shelves for a cloud and arrive on loan from another, so the three stocks’ total can change with no book bought or lost; the lab’s check for at least three transfers finds none. SF 08’s and SF 09’s briefs require transfers so that nothing appears or vanishes between stocks.
  • A material delay confused with a signal delay. In the understanding check about printer paper, the five days between ordering a box and its arrival is a material delay chosen as the signal delay. SF 10 marks the year or two between heavier workload and more resignations as a signal delay.
  • A delay drawn for the time material spends in a stock. In the reading’s third question, a material delay and a signal delay are the wrong choices for the wait at the fax stage: the stocks hold it, and a delay on the flow would count it twice.
  • A stock read as highest when its inflow is fastest. In the chapter’s Common misreading, this is the correlation heuristic (Cronin, Gonzalez and Sterman, 2009), with the study’s department store task. In the understanding check about a chairlift, at 9:30, when skiers join fastest is this reading.
  • A loop read as holding material. In the reading’s first question, in the loops B1 to B4 is a wrong choice for where a patient’s two hours are spent: a loop sets how fast patients leave a stage, and only stocks hold them.

Exercises to set

Section titled “Exercises to set”

The session goes from two loops through one stock, through a published aging chain, to an aging chain of seedlings; capacity, evidence coding, a complete model and the case come afterwards.

For a session

Afterwards

Sources

Section titled “Sources”