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Controls affecting exchangeable adjustments

 

Force use of exchangeability routines
 
tex2html_wrap_inline33790 tex2html_wrap_inline33790 Usage

tex2html_wrap_inline33806 tex2html_wrap_inline33806

The exchangeable  control can be used to force the exploitation of exchangeability in the special circumstances where (a) the sample size (fictitious or actual) is unity; and (b) beliefs specified for exchangeable situations exist. Ordinarily a sample size of unity doesn't require these beliefs for the evaluation of the adjustment. Use of this control implies that the modelvar  control also will be referenced. This method of forcing the exploitation of exchangeability is not available for the iterative adjustment algorithm.

When this method is used, then all the features commonly available to exploit exchangeability are available even though the original sample size was unity.  

Set fictitious sample size
 


tex2html_wrap_inline33790 tex2html_wrap_inline33790 Usage

  • BD>control  obs =E tex2html_wrap_inline33712 where E is any valid equation which, when rounded, results in a positive integer.

  • the default value is tex2html_wrap_inline41866 .

tex2html_wrap_inline33806 tex2html_wrap_inline33806

The obs  control determines the fictitious sample size that the program assumes when it is preparing an adjustment in the case that no actual data is available, or in the case that the usedata  control is switched off. If a mistake is made in defining the equation, and an error is reported, then the previous value will be retained.  

Use available data
 


tex2html_wrap_inline33790 tex2html_wrap_inline33790 Usage

  • BD>control  -usedata  tex2html_wrap_inline33712 switches off the control.

  • BD>control  usedata  tex2html_wrap_inline33712 switches on the control.

  • default setting is ON.

tex2html_wrap_inline33806 tex2html_wrap_inline33806

The usedata  control determines whether the command uses any available data to produce observed adjustments. When the control is on, the program always tries to use data if available. If no data is available, or if the control was switched off, there is no attempt to use data, and the prospective sample size used is the one set by the obs  control.  

Using special algorithms for exchngeable adjustments
 


tex2html_wrap_inline33790 tex2html_wrap_inline33790 Usage

  • BD>control  -matchcd  tex2html_wrap_inline33712 switches the control off.

  • BD>control  matchcd  tex2html_wrap_inline33712 switches the control on.

  • the default is OFF.

tex2html_wrap_inline33806 tex2html_wrap_inline33806

The setting of the matchcd  control determines whether or not mean component and predictive component exchangeable adjustments carried out via the ADJUST:  command are computed using special algorithms. We recommend that the special algorithms should be used as this avoids much unnecessary calculation. Except in the case of rank degeneracy, the results will be identical. In the case of rank degeneracy, the special algorithms ensure that the canonical directions for mean and predictive component adjustments are identical except for a normalising constant; this typically gives canonical directions for the mean component adjustment which are valid but different (because of non-uniqueness) to the directions computed by the default algorithm.  


next up previous contents index
Next: Data controls Up: Controls Previous: Controls affecting default expectation

David Wooff
Wed Oct 21 15:14:31 BST 1998