ABSTRACT
How and why do errors and biases creep into estimates and forecasts? Are there patterns of bias? Is it possible for a trained professional to anticipate and pre-emptively to adjust for certain types of predictable bias? This chapter is concerned with exploring and answering those questions. Two sources of bias are identified: people’s own inherent errors and biases; and the biases which are introduced when people talk to or report to each other, especially when the reporting is up and down a managerial or power hierarchy. Patterns may be identified in both types of bias. We preface the material on biases with a brief consideration of the nature of rules of thumb.
