Scientific authorship: including a former lab member who collected (unused) pilot data? I am working on a manuscript of a project that I am first author on, and am wondering whether it is proper to include person X. X has been gone from the lab for 3 years, and none of her data is in the manuscript or really informed the conclusions. However, my experimental design (for one figure out of 8) is very similar to her original plan, although the analysis is different. It's not clear if the original idea was X's, or my PIs (it was a pretty natural extension from a paper we read in journal club). Any advice about whether X should be a coauthor? Does anyone have any examples of this happening, and what was the outcome from each perspective? 

Update: thank you for all the input! To clarify:
1. My PI was actually the one who asked ME for my opinion in this situation - I think she was on the fence. But you're right that it is her job to make the final call, she was there when the original pilot experiments were performed.


The experimental tools were not new, they are common/published already. The details of the design (I.e. vary x in increments of 5) were the former student's
Looks like we are planning (at least at the conference stage, could always change when paper is closer to submission) towards not including X
There are two key questions, as I see it.  The first is whether the experimental design you used was originated by the former student.  If it was the PI's idea (or somebody else's), and the student merely implemented it, that the former student does not need to be an author.  If, on the other hand, the apparatus and techniques were truly originated by the former student, there may be a strong case for making them an author.  You should ask the PI specifically about who designed the experiment (as well as consulting them about the whether the previous student should be a coauthor; the PI is likely the best person to evaluate whether the student made a meaningful contribution to the current paper).

If it is established that the old student did originate the experimental arrangement, there is then a second question:  Was this experimental design already used as the basis for a published paper with that student as an author?  If there was already a paper on the older results, then the student has already received credit for designing the experimental setup.  In that case, you can cite the older paper as originating the methodology, and the former student does not need to be an author on papers describing further developments made after they left.