R-Bar - Range
Part of most of any statistical
process control plan. Range is the spread of the observations, (subgroups),
using stratified sampling and
usually a random sampling plan.
It is calculated by subtracting the lowest
sample from the highest sample in the
observation set. R-Bar, is the average range of a set observations, (subgroups).
This data is typically charted on a line control
chart with the center line being R-Bar, (an average of the ranges),
and upper control limits and lower
control limits. (see X-Bar
and Range, (R-Bar), Control Charts for a pictures and additional
information of these types of charts)
Range measures the variability
of the process.
N is the largest sample in the observation set
n is the smallest in the observation set
Example:
Range1 - (.051 - .049) = 0.002
Range2 - (.052 - .049)= 0.003
R-Bar = (Range1 + Range2) / 2 =
0.0025
R-Bar = 0.0025
For an example of a R-Bar charts see our ZeroRejects
features page. It makes doing six sigma
and statistical
process control charts easy and it only costs $150.00.
