I need to convert choice data that is saved in an SPSS file to .cho so I can analyze in CBC/HB. Can you explain the layout of a .cho file so I can figure out the best way to do this?
I think trying to write out a .cho is the overly complicated way of approaching it (.cho file being a unique layout that combines design and answer information that most of our analysis software supports). Both SSI Web and CBC/HB version 5 support CSV imports. It will be much easier, for example, for you to format your respondent answers in the following layout:
Resp#,Version#,Choice in task 1, Choice in task 2, etc.
and then provide that file with a design to CBC/HB directly, or first import the design into an SSI Web survey (if you used SSI Web to generate the design) and then import the answers in via the Paper and Pencil module.
If you want to have SSI Web do it, you would make a study with a CBC exercise and add in your attributes and levels. In all the design settings you would match the design files you have. Then you would import one of your designs into SSI Web. Under the Field menu, you would then create a paper and pencil template file, which will have the layout above and name each column according to your design. Import that file, then turn around and export it back out as a cho file for CBC/HB.
For the CBC/HB v5 approach, it’s the same thing, you just provide it with the CSV files of answers and a design directly. There is a help file called "Creating Your Own Datasets in .CSV Format" in the CBC/HB Help Manual that walks you through it.
If you are using older software that does not support CSV files, then there will be an Appendix in the CBC/HB help files describing the layout of the .cho file.