Quality and Reliability Methods - SAS

Chapter 10 Variability Charts 161
Variance Components
Table 10.1 Models Supported by the Variability Charts Platform
Model Factors Effects in the model
Crossed 1
2
3
4
5
Nested 1
2
3
4
A
A, B, A*B
A, B, A*B, C, A*C, B*C, A*B*C
A, B, A*B, C, A*C, B*C, A*B*C, D, A*D, B*D, A*B*D, C*D,
A*C*D, B*C*D, A*B*C*D,
and so on, for 5, 6 factors
A
A, B(A)
A, B(A), C(A,B)
A, B(A), C(A,B), D(A,B,C)
Crossed then Nested 3 A, B, A*B, C(A,B)
Nested then Crossed 3 A, B(A), C, A*C, C*B(A)
Variance Component Method
The platform launch dialog enables you to choose the method for computing variance components. Click
the Analysis Settings button to get the following dialog.
Figure 10.9 Variance Component Options
Choose best analysis (EMS, REML, or Bayesian) is the default option. The logical flow of this option
is described below:
– If the data are balanced, and if no variance components are negative, the EMS (expected mean
squares) method is used to estimate the variance components.