Cognitive BiasesPublic knowledge library

Practice Lab

Project estimation & delivery

Learn to connect a practical check with the evidence-reviewed lens behind it. A real situation can involve several patterns, so each exercise asks for the best first lens among the listed options, not a diagnosis.

How to use this set

Read the check. Choose a lens. Then inspect the evidence.

Use these evidence-reviewed lenses when setting a deadline, estimating effort, discussing delivery risk, or learning from a project that finished later than expected.

Read the full decision guide before or after the set.

Exercise 1 of 6

In project estimation & delivery, which lens does this check belong to: “What happened on the most comparable completed work, and why should this case be faster or slower?”

  1. Planning Fallacy
  2. Anchoring Effect
  3. Subadditivity Effect
Show the best first lens

Planning Fallacy

What happened on the most comparable completed work, and why should this case be faster or slower?

Evidence note The planning fallacy is a well-documented tendency for people to predict their own task completion times too optimistically. The effect has been observed across different kinds of tasks, but it is not a rule that every plan will run late. Project overruns can also come from changing scope, dependencies, incentives, poor data, deliberate underestimation, or genuinely unusual events, so a late project should not automatically be diagnosed as a planning fallacy.

Read the evidence review · Open the decision guide

Exercise 2 of 6

In project estimation & delivery, which lens does this check belong to: “Which early number is shaping this estimate, and what would we estimate if we had not seen it first?”

  1. Subadditivity Effect
  2. Availability Heuristic
  3. Anchoring Effect
Show the best first lens

Anchoring Effect

Which early number is shaping this estimate, and what would we estimate if we had not seen it first?

Evidence note Anchoring is a well-supported effect in which an initial numerical value can pull a later estimate toward it. A 2026 meta-analysis covering 2,601 effect sizes found a large overall effect, but also substantial variation across studies. The effect should not be treated as a rule that every number changes every judgment: incidental anchors, anchors from a different dimension, clearly random values, incentives, and some debiasing conditions were associated with smaller or null effects.

Read the evidence review · Open the decision guide

Exercise 3 of 6

In project estimation & delivery, which lens does this check belong to: “Does the risk estimate change when we unpack the main ways the project could be delayed?”

  1. Hindsight Bias
  2. Subadditivity Effect
  3. Availability Heuristic
Show the best first lens

Subadditivity Effect

Does the risk estimate change when we unpack the main ways the project could be delayed?

Evidence note People often give a larger total probability when an event is unpacked into separate possibilities than when the same event is judged as one packed category. The effect is not universal: how the possibilities are described and how typical they are can change or even reverse an unpacking effect.

Read the evidence review · Open the decision guide

Exercise 4 of 6

In project estimation & delivery, which lens does this check belong to: “Are we using a vivid recent project as the baseline because it is representative, or simply because it is easy to remember?”

  1. Availability Heuristic
  2. Hindsight Bias
  3. Escalation of Commitment
Show the best first lens

Availability Heuristic

Are we using a vivid recent project as the baseline because it is representative, or simply because it is easy to remember?

Evidence note Availability is a judgment heuristic: people can use how easily examples or scenarios come to mind when estimating frequency or probability. That shortcut is not automatically an error because memorable or accessible examples can correlate with real frequency. Bias appears when accessibility is driven by factors that are not diagnostic of the quantity being judged.

Read the evidence review · Open the decision guide

Exercise 5 of 6

In project estimation & delivery, which lens does this check belong to: “What did the original estimate and assumptions actually say before we knew the delivery result?”

  1. Escalation of Commitment
  2. Planning Fallacy
  3. Hindsight Bias
Show the best first lens

Hindsight Bias

What did the original estimate and assumptions actually say before we knew the delivery result?

Evidence note Knowing an outcome can make the outcome look more predictable in retrospect. The effect has been studied for decades and across many settings, but it does not mean that every confident explanation after an event is biased.

Read the evidence review · Open the decision guide

Exercise 6 of 6

In project estimation & delivery, which lens does this check belong to: “If we were deciding only about the remaining work today, would we still choose the same next step?”

  1. Anchoring Effect
  2. Escalation of Commitment
  3. Planning Fallacy
Show the best first lens

Escalation of Commitment

If we were deciding only about the remaining work today, would we still choose the same next step?

Evidence note Sunk-cost effects and escalation of commitment overlap but are not interchangeable. Sunk-cost research asks whether irrecoverable prior investments influence current choices. Escalation of commitment describes persistence or additional resource allocation to a failing course of action and can also be driven by personal responsibility, self-justification, project structure, and other factors.

Read the evidence review · Open the decision guide