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Every box on the influence diagram is a node. Its shape and colour tell you what kind of node it is. This page shows each kind, taken from the Halden Foods case.
This page is part of step 2. For how to add and connect boxes, see How to build an influence diagram.

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The seven kinds at a glance

Decision

The choice you are making. One per model.

Setting of the decision

A number that changes with the option you pick.

Uncertain estimate

A number you are not sure about, shown as a range.

Fixed value

A number you treat as certain.

Calculation

A number worked out from other boxes.

Outcome

What you use to judge the options.

Module

A folder that holds its own boxes.

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Decision

The decision box: Should Halden Foods launch the Nova range, with a Showing menu set to No-go
What it is. The question you are answering. Its options are the choices you compare, such as No-go, a full launch, or launching in two regions first. How to spot it. A green rectangle with a Showing menu. The menu picks which option the numbers on the diagram are shown for. When to use it. You do not add it. Every model has exactly one. You set its options when you frame the decision. Halden Foods example. “Should Halden Foods launch the Nova range, and how?” Switch Showing from No-go to another option and every calculation on the diagram updates.

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Setting of the decision

The setting We launch Nova, with the value 0 and the line 0, 1, 1, 1 showing its value for each option
What it is. A number that the chosen option sets for you. It is how an option reaches the rest of the model. How to spot it. A white rectangle with a double green border. It shows the value for the option on show, and one line with the value under every option. The current option is in bold. When to use it. Use it when options differ in a clear way, such as on or off, a spend, or a number of regions. Other boxes use it in their formulas. Halden Foods example. “We launch Nova” is 0 for No-go and 1 for the other three options. “Extra hiring and a pilot” is 1 only for the option that includes them.

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Uncertain estimate

The uncertain estimate Customer demand against plan: 95 percent, range 70 to 130 percent, with a faint histogram behind it
What it is. A number the result depends on and that you cannot pin down. You give it a range, not a single guess. See Describe estimates. How to spot it. A yellow capsule. The big number is the most likely value. Under it is the range, and a faint histogram behind it shows how likely each value is. When to use it. Whenever you would otherwise write “about” or “it depends”. Prices, demand, delays and costs are the usual ones. Halden Foods example. “Customer demand against plan” is most likely 95%, but could be anywhere from 70% to 130%.
A box that still has no estimate shows Estimate needed in a dashed outline. Fill it in before you run the simulation.

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Fixed value

The fixed value Build budget: 1.2M, labelled fixed
What it is. A number held at one value. It adds no uncertainty. How to spot it. A grey box with cut corners. It is labelled fixed under the number. When to use it. For things you know, or that someone has decided: a budget, a date, a contract price, last year’s actuals. Halden Foods example. “Build budget” is fixed at $1.2M. “Chilled ready-meal market” is fixed at 400M.
If you are unsure whether a number is really certain, make it an uncertain estimate. A narrow range costs little and shows how much it matters.

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Calculation

The calculation Nova sales, a light blue rounded box
What it is. A number worked out exactly from the boxes that point into it. It has no range of its own, but it inherits the spread of its inputs. How to spot it. A light blue rounded rectangle. When its inputs are uncertain, it shows a range and a histogram too, as “Months to ship” does below. When to use it. To combine other boxes: sales are customers times conversion, profit is revenue minus cost. See Formulas. Halden Foods example. “Months to ship” is the development time plus any hiring delay, reduced when a pilot or extra QA is chosen.
Inspector for Months to ship, Overview tab, with a plain-language description of how it is calculatedInspector for Months to ship, Advanced tab, showing the identifier and the stored formula

Select a calculation to see its inputs. The inspector explains how it is calculated; the Advanced tab shows the formula.

A calculation with no formula yet shows No formula yet. One that is missing an input shows Waiting on an input.

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Outcome

The outcome Revenue growth, a dark purple hexagon with a small diamond
What it is. A result you use to judge the options. Each outcome is judged on its own. Meerie does not blend them into one score. How to spot it. A dark purple hexagon with a small diamond. The diamond means a higher or lower value is better, as set in your win criteria. When to use it. Add one for every measure the decision is judged on. Keep the list short. See win criteria. Halden Foods example. “Net value in today’s money”, “Revenue growth” and “EPS improvement” are outcomes. So are “Launch timing” and “Customer satisfaction”.

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Module

The module Customers, a white box with a folder icon, 2 inside, and an Open button
What it is. A folder of boxes. It keeps a big diagram readable. It changes only the layout, never the numbers. How to spot it. A white box with a thick outline, a folder icon, a count such as 2 inside, and an Open button. Open it, and use Up one level or the breadcrumb to come back. When to use it. When a diagram grows past a screen, or when a group of boxes belongs together, such as demand, delivery or money. Halden Foods example. “Customers” holds two boxes: an uncertain customer satisfaction score and the calculation that feeds the outcome. “Money” holds eight.

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Which one do I need?

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Arrows

Arrows show what feeds what. An arrow points from an input to the box that uses it.
Months to ship selected, with blue arrows from the two boxes it uses and a grey arrow elsewhere

Months to ship is selected. The blue arrows come into it from the boxes it is calculated from.

  • Direction. The arrow head sits on the box that is calculated.
  • Selecting a box. Click one and its inputs are drawn in blue. What it feeds is drawn in orange. Other arrows stay grey.
  • A dashed arrow. You drew it, but no formula uses it yet. Writing the formula makes it solid.
  • Writing a formula draws the arrow. Use a box in a formula and its arrow appears. Drop it and the arrow goes.
  • Hide arrows. The Hide arrows button clears them when the view gets crowded.
Arrows here show direction only, not how strong an effect is. An older Diagram view drew arrows by direction and weight, but it is not on the diagram screen at present. To see which inputs matter most, use the results. See Reading the numbers.
Next: Set estimates