I am using SPSS to develop an Orthogonal Design. The design is a 4x3x3x3x3 (324 factors). The following sample syntax automatically generates 16 cards (I don’t have to tell it to generate that many).
My question is whether SPSS has ‘automatically calculated’ the number of cases I should be using for my design, or whether I should influence the number of cards generated. In other words, do I *need to* increase this, or can I rely on the ‘judgement’ by SPSS to use 16 cases.
Here is my plan:
ORTHOPLAN
/FACTORS=Fruit ‘Attribute1’ (1 ‘apple’ 2 ‘Orange’ 3 ‘Pear ‘ 4 ‘Raspberry’) Chocolate ‘Attribute2’ (1 ‘snickers’ 2 ‘wispa’ 3 ‘twix’) Pizza ‘Attribute3’ (1 ‘Margherita’ 2 ‘plain’ 3 ‘vegetable’) drink ‘attribute4’ (1 ‘coke’ 2 ‘pepsi’ 3 ‘water’) price ‘attribute5’ (1 ‘cheap’ 2 ‘not cheap’ 3 ‘expensive’)
/OUTFILE=’a:plan.sav’
/MIXHOLD YES.
p.s. I understand that I should add some ‘holdout cases’ (I will do that in my final study).