X Bar  Mean  Average
X Bar is an average of a sample.
It is the arithmetic mean. It is calculated by adding the observation, (subgroup
using stratified sampling),
values and dividing by the total number of samples. This data is typically
charted on a line control chart with the
center line being X Double Bar, (an average of the averages), and upper
control limits and lower control
limits. You can also use PreControl
to establish control limits.
We use averages because they are more
susceptible to change than single values. To see how to use this chart,
see statistical
process control overview and the XBar
and RBar explanation pages.
x is an individual observation
n is the total number of samples
X
Bar 
= 
^{x}1
+ ^{x}2 + ^{x}3 + ^{x}4 .... ^{x}n 

n 
Example:
X Bar = (.05 + .05 + .051 + .049 + .05) /
5
X Bar = .05
For an example of a X Bar charts see our ZeroRejects
features page. It makes doing statistical
process control and six sigma
charts easy. And
at only $150.00, (USD), our software can get you going quickly.