If respondents back up in a survey (or are skipped backward) to re-answer a previous question, answers to the later questions (which are now only conditionally valid) are thrown into "limbo" status and are not saved in the final data record (though they are available in the history table). Respondents must re-answer those questions.
Respondents can back up in a survey by either clicking the browser's back button (or the Previous button) or by being skipping back to a previous question.
Example:
As respondents answer questions, the answers are recorded in the database like this:
Q1, 5
Q2, 3
Q3, 2
Q4, 13
Here is an example of backing up and re-answering a previous question:
Q1, 5
Q2, 3
Q3, 2
Q4, 13
Q2, 7 (This respondent has backed up and re-answers Q2)
The data are then cleaned and old data (limbo data) are preserved in the history table. Now the data record would contain:
Q1, 5
Q2, 7
and the respondent needs to answer Q3 and Q4 again.