The questionnaire system uses specific codes to represent different types of missing responses:
-99 (Skipped): When a participant encounters a question but chooses not to answer it (e.g., leaves it blank), the system records "-99".
-77 (Filtered Out): When a question is not displayed to a participant due to filter conditions, the system records "-77".
Setting Up Filter Conditions:
hide if [question] == -99
hide if [question] == -77
hide if [question] == -99 OR [question] == -77
.
If you only use positive integers as response values, you may also be able to simplify the condition as hide if [question] < 0