Optimistic Probability Bias

Optimistic Probability Bias is the specific tendency to overestimate the probability of favourable events and underestimate the probability of unfavourable ones. While Optimism Bias is a broad disposition, Optimistic Probability Bias operates at the level of explicit probability estimates — when asked to assign a number to the chance of success or failure, people systematically skew toward the optimistic end. A founder estimating a 70% chance of closing a deal is often operating closer to 40%. A team projecting a 90% probability of hitting a milestone is often at 60%. The bias is compounded in business because probabilities are rarely checked against outcomes — you launch the product, it succeeds or fails, and the original probability estimate is never audited. Without feedback loops, optimistic probability estimates persist uncorrected, leading to systematically miscalibrated risk assessment across the organisation.