Specifically, the normalization of deviance process in Challenger Launch Decision involved a 5-step process:
Signal of potential danger
Official act acknowledging potential danger
Review of the evidence
Official act indicating the normalization of deviance (i.e. accepting the risk)
Shuttle launch
The key thing that Vaughan identifies is that in every iteration of the above cycle, the standard that was compared against was the output of the previous iteration. Because of this, the notion of what was “acceptable” joint rotation subtly shifted over time, from what a conservative standard in 1977 to a very risky one 1986. The problem was that NASA was updating its beliefs about what was acceptable O-ring performance, but, as an organization, was not realizing that it had updated. As a result it drifted in an uncontrolled manner from its original standards, and thus signed off as safe a system that was, in retrospect, a disaster waiting to happen.
Normalization of deviance is a difficult problem to combat, because the process that leads to normalization of deviance is also the process that leads to helpful and beneficial updates about the state of the world. I would suggest that some normalization of deviance, within limits is acceptable. The world is not always going to be what your model says it will be, and you have to have some leeway to adapt to circumstances that aren’t what you were expecting. However, when doing so, it’s important to ensure that today’s exception remains an exception, and that the next time deviance occurs, it’s checked against the original standard, not an updated standard that results from the exception process.
Specifically, the normalization of deviance process in Challenger Launch Decision involved a 5-step process:
Signal of potential danger
Official act acknowledging potential danger
Review of the evidence
Official act indicating the normalization of deviance (i.e. accepting the risk)
Shuttle launch
The key thing that Vaughan identifies is that in every iteration of the above cycle, the standard that was compared against was the output of the previous iteration. Because of this, the notion of what was “acceptable” joint rotation subtly shifted over time, from what a conservative standard in 1977 to a very risky one 1986. The problem was that NASA was updating its beliefs about what was acceptable O-ring performance, but, as an organization, was not realizing that it had updated. As a result it drifted in an uncontrolled manner from its original standards, and thus signed off as safe a system that was, in retrospect, a disaster waiting to happen.
Normalization of deviance is a difficult problem to combat, because the process that leads to normalization of deviance is also the process that leads to helpful and beneficial updates about the state of the world. I would suggest that some normalization of deviance, within limits is acceptable. The world is not always going to be what your model says it will be, and you have to have some leeway to adapt to circumstances that aren’t what you were expecting. However, when doing so, it’s important to ensure that today’s exception remains an exception, and that the next time deviance occurs, it’s checked against the original standard, not an updated standard that results from the exception process.