1.
Exploratory Data Analysis
1.2.
EDA Assumptions
1.2.5.
Consequences
1.2.5.3.

Consequences of NonFixed Variation
Parameter


Variation Estimate

The usual estimate of variation is the standard deviation
$$s_Y = \frac{1}{\sqrt{(N1)}} \sqrt{\sum_{i=1}^{N}
{(Y_i  \bar{Y})^2}}$$
from N measurements Y_{1},
Y_{2}, ... , Y_{N}.

Consequences of NonFixed Variation

If the run sequence plot does not support the assumption of
fixed variation, then
 The variation may be drifting.
 The single variation estimate may be meaningless
(if the process variation is drifting).
 The variation estimate may be poor.
 The variation estimate may be biased.
