What Is Confirmation Bias?
Confirmation bias is a type of cognitive bias that leads people to seek, interpret and remember information in ways that confirm what they already believe, while giving less weight to evidence that contradicts it.
In Practice
On projects, confirmation bias can make a team over-trust a favored estimate, dismiss early warning signs, or read status data selectively. Countermeasures include seeking disconfirming evidence, inviting dissent, using independent reviews and pre-mortems, and grounding decisions in objective measures rather than impressions.
PMBOK 8 Context
Awareness of cognitive biases such as confirmation bias supports sound decision-making across the PMBOK Guide, 8th Edition, particularly in the Uncertainty and Measurement performance domains. It is closely tied to honest performance measurement.
FAQ
Can you eliminate confirmation bias? Not entirely — but structured techniques and diverse perspectives significantly reduce its effect.
How does it relate to vanity metrics? Both let a team feel validated without genuine evidence; guarding against one helps guard against the other.
Author: Tom, PMP-certified since 2004. Last updated: July 2026. Aligned with the PMBOK Guide, 8th Edition.