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

## Consequences of Non-Fixed Variation Parameter

Variation Estimate The usual estimate of variation is the standard deviation
$$s_Y = \frac{1}{\sqrt{(N-1)}} \sqrt{\sum_{i=1}^{N} {(Y_i - \bar{Y})^2}}$$
from N measurements Y1, Y2, ... , YN.
Consequences of Non-Fixed Variation If the run sequence plot does not support the assumption of fixed variation, then
1. The variation may be drifting.

2. The single variation estimate may be meaningless (if the process variation is drifting).

3. The variation estimate may be poor.

4. The variation estimate may be biased.