Should I include a publication where I'm only acknowledged (and not one of the authors) in my CV?
I've never seen anything like this on a CV.

If you have other publications, I certainly wouldn't include this. It would look like you are trying too hard to find something to put on your CV, which could do more harm than good. Let your publications stand for themselves.

One thing you could do when describing the various jobs you've had, is to include the statistical analysis work in the description of the activities you performed in that job. You could also mention it in the cover letter, if it is relevant for the job. Finally, do bring it up in the interview as an example of how you work in a collaboration.