5.2 Case analysis module: therac-25

Computer Ethics

Case Module Template

By William J. Frey

Module Introduction:

The Therac-25 case is what Huff and Frey call a thick, historical, evaluative, big news and bad news case. Tackling cases of this complexity requires both careful thought and considerable skill. Especially important is the ability to sift through the case details, documents, and conflicting narratives. The purpose of this module is to provide students with a structure to tackle big, long, and complicated cases. Students will receive frameworks to help them structure the case's ethical and social problems. They will also be provided with decision points that will help them to enter into the case and take up the standpoint of a participant. The module presented below can be linked to materials that can be found at www.computingcases.org. Nancy Leveson, in Safeware:System Safety and Computer (515-553), also provides an excellent and comprehensive account. Excellent advice on how to teach the case, updated information, and clear explanations of the programming errors are provided by Chuck Huff and Richard Brown in "Integrating Ethics into a Computing Curriculum: A Case Study of the Therac-25." The materials posted at Computing Cases were all developed through NSF projects DUE-9972280 and DUE 9980768.)

The module presents the case abstract and timeline. It then refers students to computingcases.org where theywill find the case narrative, history, and supporting documents that provide background information necessary for analysis. Thecase abstract and timeline introduce students to the basic outlines of the case. The accompanying decision point taken from the caseprovides students with the necessary focus to carry out an in-depth analysis. Students respond to the decision-point by working throughthe four stages: problem specification, solution generation, solution testing, and solution implementation.