Exclusive "None of the above" option

Question

[copied from GT FB group]

I'm doing a multi-choice question (checkboxes) and would like to make "None of the above" exclusive so that other items on the list cannot be checked. It's not critical, but is that possible?

Answer 1

Consider not having a "None of the above option" and instead just putting a

*tip: if none of the options apply, leave them all unchecked. 

In other words, "None of the above" is already represented very naturally by them simply not checking any options listed.

Or if you include it and people select more than one then you could exclude them from the dataset for low quality. e.g.

*question: Pick things
    Thing 1
    Thing 2
    None of these
    *save: things

*if: ("None of these" in things) and (things.size > 1)
    >> low_quality = 1