There are several approaches to this. You will find a few discussions on the forum here as well. How I would do it:
I would create 2 surveys, as you suggested. One with only the research, the other one with the personal data. However, if you want to prevent that some clever people generate more than one entry in the survey for the participation, you need to connect the 1st survey with the second survey. You wanted to do this via a generated code, but you would need to save this code in the first survey as well, otherwise you won't be able to confirm that this person has taken the survey. To be able to do this, you need to be able to connect the first survey somehow with the second survey and at this point it means that the survey is not 100% annonymous based on purely technical terms. However, in market research for example, surveys are rarely 100% annonymous from a technical standpoint. However, companies adhering to the market research standards (e.g. ESOMAR code of conduct), will guarantee that they will not connect results with personal data, which is the important part. However, to be able to send a prize but at the same time avoid fraud you need to have a certain control.
I would create 2 surveys, as you suggested. One with only the research, the other one with the personal data. However, if you want to prevent that some clever people generate more than one entry in the survey for the participation, you need to connect the 1st survey with the second survey. You wanted to do this via a generated code, but you would need to save this code in the first survey as well, otherwise you won't be able to confirm that this person has taken the survey. To be able to do this, you need to be able to connect the first survey somehow with the second survey and at this point it means that the survey is not 100% annonymous based on purely technical terms. However, in market research for example, surveys are rarely 100% annonymous from a technical standpoint. However, companies adhering to the market research standards (e.g. ESOMAR code of conduct), will guarantee that they will not connect results with personal data, which is the important part. However, to be able to send a prize but at the same time avoid fraud you need to have a certain control.
