z-value

a standardized value formed by subtracting the mean and then dividing this difference by the standard deviation. A Z value is a data point's position between the mean and another location as measured by the number of standard deviations. Z is a universal measurement because it can be applied to any unit of measure. Z is a measure of process capability and corresponds to the process sigma value that is reported by the businesses. For example, a 3 sigma process means that three standard deviations lie between the mean and the nearest specification limit. Three is the Z value.

Zst

Often called 'benchmarking sigma' or 'sigma value'. The distribution, or variation, or spread around the mean(average) value of any process or procedure. For a business process, the sigma value indicates how well that process is performing, i.e. Zst is a short-term capability index of a process or a part(Zst=1.0 is bad, Zst=4.0 is mediocre performance, Zst=6.0 is considered 'worldcalss').

Z Shift

Z shift is the difference between ZST and ZLT. The larger the Z shift, the more you are able to improve the control of the special factors identified in the subgroups.

Z Score

A measure of the distance in standard deviations of a sample from the mean.

Z lt

Z long term (ZLT) is the Z bench calculated from the overall standard deviation and the average output of the current process. Used with continuous data, ZLT represents the overall process capability and can be used to determine the probability of making out-of-spec parts within the current process.

Z bench

Z bench is the Z value that corresponds to the total probability of a defect.