Nate Silver, the well known statistical reporter compared the performance of the main polling organizations forecasting elections. The results of his comparison are shown in the chart. What is shown is the average error of the pollsters predictions calculated for the number of polls they did. For example, Quinnipac conducted 21 polls and on average [...]
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 [...]
A hypothesis is a supposition made as a basis for research or reasoning without regard for its truth. So says the Oxford dictionary. What starts the hypothesis testing process is just such a supposition. In the justice system example we made, there is a supposition on the part of law enforcement that the apprehended person [...]
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 [...]
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 [...]
