I'm doing a pharma study with a large number of SKUs. Each respondent allocates 100% of future prescriptions among all alternatives. I plan to analyze the data using CBC HB software.
There are two attributes - product and price.
Due to the study specifics, not all of the SKUs (products) are going to be shown to each respondent (not only because they are unattractive for some of them, but also because they are inaccessible). Therefore, something like an evoked set (consideration set) of SKUs is going to be formed for each respondent.
The questions is, what do I need to write down into the .chs file for the SKUs not present in a respondent's consideration set?
1) First, I could include all of SKUs into all respondent records in the .chs file and artifically insert zeroes as points allocated to SKUs not shown to a respondent. I suppose this is going to decrease utilities of SKUs rarely accessible (which seems to be good idea for predicting market share, not the share of preference). Furthermore, I would need to enter some price levels for such SKUs as well, which would decrease the utilities of these price levels either.
2) Secondly, I could simply exclude irrelevant SKUs from respondent's records, which would result into different number of concepts per tasks for each respondent. This approach seems more logical to me, but I'm not sure if it's correct in terms of the way CBC HB treats .chs data?
I've noticed that CBC HB utility estimation has no problem with such .chs files, but I still have doubts.