It Will Never Work in Theory

Software development estimation biases: the role of interdependence

Posted Jun 12, 2012 by Jorge Aranda

| Controlled Experiments | Estimation |

Magne Jørgensen and Stein Grimstad. "Software development estimation biases: the role of interdependence." TSE 2012 38(3).

Software development effort estimates are frequently too low, which may lead to poor project plans and project failures. One reason for this bias seems to be that the effort estimates produced by software developers are affected by information that has no relevance for the actual use of effort. We attempted to acquire a better understanding of the underlying mechanisms and the robustness of this type of estimation bias. For this purpose, we hired 374 software developers working in outsourcing companies to participate in a set of three experiments. The experiments examined the connection between estimation bias and developer dimensions: self-construal (how one sees oneself), thinking style, nationality, experience, skill, education, sex, and organizational role. We found that estimation bias was present along most of the studied dimensions. The most interesting finding may be that the estimation bias increased significantly with higher levels of interdependence, i.e., with stronger emphasis on connectedness, social context, and relationships. We propose that this connection may be enabled by an activation of one's self-construal when engaging in effort estimation, and a connection between a more interdependent self-construal and increased search for indirect messages, lower ability to ignore irrelevant context, and a stronger emphasis on socially desirable responses.

Researchers know that estimates of software development effort can be biased pretty easily by anchors and by irrelevant information. An important question, though, is whether these biases occur due to purely cognitive reasons or due to a desire to please and to connect with others. Jørgensen and Grimstad help answer this question, by getting hundreds of paid developers from several countries to participate in an experiment. Some of their findings:

Bias in effort estimation seems to be present for developers from all the countries studied. We were unable to find strong and systematic differences between countries or regions (Eastern Europe and Asia). (...)
In spite of the lack of any strong and systematic difference between the countries and regions, there may be culturally related variables that are useful for understanding the mechanisms by which estimation biases occur. In particular, a developer's level of interdependence (emphasis on connectedness, social context, and relationship) seems to be connected systematically with how much he or she was affected by irrelevant and misleading information and with lower effort estimates.

In other words, they found that everyone (that would include you and your peers) seems susceptible to estimation biases, that people with greater levels of "interdependence" (those that give greater weight to relationships and connectedness) are more subject to bias, and that despite this, cultural differences by country do not seem to play an important role in estimation bias. The best thing you can do, in any case, is to try to shield estimators from anchors and other sources of bias as much as possible.

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