Root Cause Analysis

8 • Root Cause Analysis

variable. In the rust study example, the treatment variable rust inhibitor

was not properly controlled; various concentrations of rust inhibitor were

unknowingly used, and the results of the study were masked by the varia-

tion in the rust inhibitor.

Feynman (1988) points out the need for objectivity in using the scientic

method. He warns experimenters to be careful of preferring one result

more than another and uses the example of dirt falling into an experi-

ment to illustrate this hazard; the experimenter should not just accept the

results that he or she likes and ignore the others. e favorite results may

just be t ...