|Title||The probable, the uncertain, and the hypothetical: Problems of assessment and communication|
|Afilliation||, Software Engineering|
|Publication Type||Talk, keynote|
|Year of Publication||2016|
|Location of Talk||Concept Symposium 2016 Stavanger|
Inexact estimates of future outcomes and past events can be communicated in a variety of ways: Numerically, as probabilities or as uncertainty (confidence) intervals, and verbally, in words or phrases denoting likelihoods and doubts. We discuss in this paper some general issues and problems with both kinds of estimates for assessors, communicators and recipients of the communication, illustrated by current research within the psychology of judgment and decision making.
Subjective probability estimates of multiple outcomes do not add up to 100%, and are often assessed by a simple proximity heuristic, sometimes making hypothetical outcomes (what could have happened, but did not) more imaginable and likely in retrospect
Subjective uncertainty intervals are typically too narrow, and appear insensitive to the degree of confidence required
Revised forecasts are perceived as trends that will continue into the future
Single bound ranges (“more than 5 mill”, “less than 10 percent chance”) imply qualitative messages in addition to the quantities involved (e.g., opinions, recommendations, and the existence of trends)
Verbal phrases are of two kinds: Positive (possible, a chance) or negative (not certain, unlikely). They are directional, by asking recipients to consider either the occurrence or the non-occurrence of a target outcome.
Communicators regularly use the modal verb can to describe extreme (top) outcomes, regardless of their probabilities. However, such estimates are often perceived by recipients to denote expected rather than extreme values, leading to exaggerated claims.
These judgmental aspects of words and numbers are often neglected, but should be taken into account in all stages of project management.