Specifying the within subject design
If you could convince yourself that the data is correctly imported, you can proceed to specify your design. In the dialog that opens when you hit the 'Within subject design' button, first choose whether you have one or two within subject factors. Then you proceed to assign the data that you have imported to different levels of your factors. To specify the levels of factor 1 click the F1 button. To specify the levels of factor 2, click the F2 button. To set the level of a condition for a given factor, select the condition in the list-box and use the '+' and '-' buttons to modify the level. In the subsequent analysis of the effect of a given factor, conditions that have the same level will be assumed to have the same characteristics of this factor.
Let's illustrate this. Assume you have recorded ERP data with rare and frequent stimuli in a series of subjects. Each subject performed the experiment once under drug A, once under drug B and once under drug C. We have thus 6 conditions, Rare_DrugA, Rare_DrugB, Rare_DrugC, Frequent_DrugA, Frequent_DrugB and Frequent_DrugC. There are thus a factor drug, and a factor stimulus type. Let's make drug factor 1 and stimulus type factor 2.
To specify the design, we thus have to do the following. First, check the two-factorial design check-box. Select factor 1 by clicking on the F1 button. Set all conditions belonging to drug A (e.g. Rare_DrugA and Frequent_DrugA) to the same level (i.e. to 1) using the plus and minus buttons. Set all conditions belonging to drug B to another level (i.e. to 2). Set all all conditions belonging to drug C to a third level (i.e. to 3). As name of factor one, we enter "Drug", and in the table below the name of factor 1, we label level 1 as "Drug A", level 2 as "Drug B" and level 3 as "Drug C".
Factor one is now defined. Click 'F2' to specify the levels for the second factor. In our case set all conditions belonging the rare stimulus type (Rare_DrugA, Rare_DrugB and Rare_DrugC) to the same level of factor 2 (i.e. to 1).Then, set all conditions belonging to the frequent stimulus type (Frequent_DrugA, Frequent_DrugB and Frequent_DrugC) to another value (i.e. 2). The number you use to specify the levels are not important, but your design has to be orthogonal and complete. Finally, as name of factor two, we enter "Condition", and in the table below the name of factor 1, we label level 1 as "Rare" and level 2 as "Frequent".
If there are no repeated measures, leave all conditions on the same level.
You can also exclude certain conditions from the analysis using the exclude button.