Two Statistical Disciplines, Two Different Questions: How They Differ, How They Combine, and Why an Engineer Should Master Both
The two statistical traditions that reliability engineering inherits, the quality-statistics tradition descending from Shewhart and Deming and the reliability-statistics tradition descending from Weibull, Fisher, and the post-war life-testing community, are often spoken of as interchangeable extensions of a single discipline. They are not interchangeable. They were built for different questions, they make different assumptions about the data, they use different mathematics, and they support different decisions. An engineer comfortable in both moves fluently between the shop-floor control chart and the field-fleet survival analysis. An engineer who knows only one will, sooner or later, apply the wrong tradition to the wrong problem, and the analysis will produce results that are mathematically correct and engineering nonsense.