Finds out information about aliased model terms in analysis of variance (R.W. Payne).
||Treatment model for the design|
||Block model for the design|
||Value used in the
||Design structure for the analysis|
||Factors defining the aliased model term|
When a term is aliased in an analysis of variance, it is listed in the Information summary (produced by
ANOVA [PRINT=information]) under the heading “Aliased model terms” (see the Guide to the Genstat Command Language, Part 2, Section 4.7.1). However
ANOVA does not indicate the terms with which it is aliased. This information can be obtained using procedure
The aliased term is specified by setting the
TERM parameter to the list of factors that define it. The structure of the design can be specified either by options
TREATMENTSTRUCTURE (together with option
FACTORIAL, if necessary); alternatively you can save the design structure from the original analysis and supply this using the
DESIGN option – this is the only way of specifying the design if there are weights or if the analysis is restricted. If an undeclared structure is specified for
TREATMENTSTRUCTURE are also specified), it will be set to the design structure for the analysis.
The procedure calculates a set of dummy effects for the aliased model term, and then forms and analyses a variate in which only these effects are present. The analysis detects the model terms to which the term is aliased as those that have non-zero sums of squares.
None of the options nor parameters are vectors. To indicate that the analysis is of a restricted set of units you must use the
DESIGN option to specify the design structure from the original analysis.
CAPTION 'ALIAS example'; STYLE=meta FACTOR [NVALUES=32; LEVEL=2] A,B,C & [LEVEL=4] D,Blocks & [LEVEL=8] Plots GENERATE A,B,C & D & Blocks,Plots VARIATE [VALUES=13,17,25,33,18,19,22,14,26,23,31,29,25,21,18,34,\ 23,19,33,36,25,23,29,18,31,30,37,33,29,27,20,36] Y BLOCKSTRUCTURE Blocks/Plots TREATMENTSTRUCTURE A*B*C+D ANOVA [PRINT=aovtable,information] Y CAPTION !T('The aov table and information summary show that D is aliased;',\ 'ALIAS indicates that the aliasing is with B, C and B.C ') ALIAS [BLOCKSTRUCTURE=Blocks/Plots; TREATMENTSTRUCTURE=A*B*C+D] D PRINT !T('The printout below confirms this:',\ 'D level 1 corresponds to B level 1 and C level 1,',\ 'D level 2 corresponds to B level 1 and C level 2,',\ 'D level 3 corresponds to B level 2 and C level 1,',\ 'D level 4 corresponds to B level 2 and C level 2.');\ JUSTIFICATION=left & [RLWIDTH=3; ORIENTATION=across] D,B,C; FIELDWIDTH=2; JUST=left PRINT !T('Use RESTRICT to analyse only the first 3 blocks;',\ 'the main effect D is still aliased, exactly as before...');\ JUSTIFICATION=left RESTRICT Y; Blocks < 4 ANOVA [PRINT=aovtable,information; DESIGN=DB1to3] Y CAPTION 'The design must now be specified for ALIAS using the DESIGN option.' ALIAS [DESIGN=DB1to3] D