Our user Jennifer Goede has sent us the following question:
Can you explain to me when the interview key changes? I made a list of mistakes interviewers made, with their name and ED number. However when I look the interview key up it is now allocated to another interview.
An interview key is an 8-digit number assigned to interviews on the server (for example, 12-34-56-78). Every interview on a server has a unique interview key (even when they are in different surveys). If the interview is created on the server, its interview key will never change.
Yet, some interviews are created on tablets. Clearly there is a chance that two tablets will come up with the same number, and hence the same interview key. If that happens, the interview key of the first interview to reach the server will remain, while the second one will be changed.
This change can clearly occur only once, and at a particular time: at synchronization, when the interview reaches the server.
Chances of this happening are quite large. For a survey with 100,000 interviews you will have a noticeable number of interview key changes. So any program or script dealing with interview keys should be written with expectation that this will happen, rather than with a hope that this will not.
For working with exported data, match the records in different files not on interview__key, but on interview__id variable, which is stable (never changes).