Unlikely-Optimism-The-Conjunctive-Events-Bias #

The probability of a series of conjunctive events happening is lower than the probability of any individual event. The majority of students (85% to 95%) chose the latter statement, seeing the conjunctive events (that she is both a bank teller and a feminist activist) as more probable.

Why the best laid plans often fail #

The conjunctive events bias makes us underestimate the effort required to accomplish complex plans. As Max Bazerman and Don Moore explain in Judgment in Managerial Decision Making, “The overestimation of conjunctive events offers a powerful explanation for the problems that typically occur with projects that require multistage planning. What is more likely:

• The building permits get delayed
• The building permits get delayed and the electrical goes in on schedule You know a bit about the electrical schedule. Humans make mistakes, equipment fails, technologies don’t work as planned, unrealistic expectations, biases including sunk cost-syndrome, inexperience, wrong incentives, changing requirements, random events, ignoring early warning signals are reasons for delays, cost overruns, and mistakes. In the housing example above, asking what is the frequency of having building permits delayed in every hundred houses, versus the frequency of having permits delayed and electrical going in on time for the same hundred demonstrates more easily the higher frequency of option one.