To continue, we need to define a couple of terms. The first is a probability density function and the second is a sampling distribution.A probability density function expresses a particular function in terms of integrals. Thus for a frequency distribution smoothed (over repeated sampling) to form a curve as shown below, the area under the [...]
When discussing hypothesis testing, I have, from time to time, used the example of the criminal justice system to act as a metaphor for the logic and philosophical issues involved. It remains a good way to pose the logical dilemmas and the types of errors involved and to also discuss the idea of a system [...]
Imagine you are an executive in an organization that defines quality as absence of defects. How, then, would you plan to improve quality?It’s obvious isn’t it? Spend time being clear about what are defects and what are not (via specifications), find points to check for defects and, if they are found, remove them. Institute a [...]
As we saw on Part I, there are some fundamentally flawed conceptual problems with Six Sigma and its statistical underpinnings are shaky indeed.But the aspect of Six Sigma that makes it that makes it least useful as a tool to improve competitiveness is that it is based on defect detection and elimination (reduction) and not [...]
One can hardly walk into a bookstore these days without being deluged with Six Sigma volumes of one sort or the other. It seems to be an answer for every businessman’s problem from controlling quality to designing new products to guaranteeing gleeful customers. As is usually the case, with these fads, the truth is somewhat [...]
