This question is related to missing values in the dataset that I received from the download. I noticed that there are cases in which participants received an item (based on item criteria) but did not respond, i.e., observation is NA. The strange thing is that the item is mandatory, and follow by another item that did get a response. T
Is there another reason why item responses are marked as NA - besides not marking the item as mandatory, not selecting the item based on item criteria, and participants aborting the survey before the end?
This problem applies to the VAS items in particular.