P Value Usage

My quick response is we don’t use p-values to assess the stability of a process, we use control charts to help distinguish random from non-random variation..05 is a default value, but you should not be “blinded” by it. It is completely appropriate to change that to .10 or .01 in some cases. It helps you assess risk of over reacting (rejecting the null when you shouldn’t have).Span (Range, Standard deviation, Variance and Sum of Squares) are all ways to describe variability in the data (process). Welcome to the Discussion Forum

The concept of 0.05 refers to alpha risk, which is a pretty fundamental tenet of hypothesis testing.  For any test, we state in advance how willing we are to tolerate the chance that we’ll end up rejecting the null hypothesis when we shouldn’t.  Generally speaking, classroom settings advocate an alpha risk of five percent, simply because of existing practice and norm.  However, pharmaceutical companies bringing a drug to market might have to conduct tests using an alpha of 1 percent, while a low-risk business process might opt for 10 percent.  It simply depends.
A percentile is a threshold or level in a series of ordered observations, while a percentage is simply a fraction or proportion of the series with a particular characteristic.  For example, out of 500 graduating students, students in the 95% percentile are those students in the top five percent – or the top 25 – of all 500 students based on final grade.  As another example, if 200 of these students are boys, then boys make up 40% of the class.