Removing an author from a future publication I published a conference abstract with a undergraduate student of mine as a co-author. The work was presented as a poster and the conference doesn't publish proceedings/papers. I am now planning on publishing an extended version and want to drop her as a co-author. Can I do this?

Prior to the student starting the project we discussed authorship and agreed that it was unlikely that she would contribute enough to warrant authorship on anything that came out of the study since the experiment was conceived and implemented by me and I designed the statistical analysis. At the time of the conference, the student had collected approximately 1/4 of the data on the poster and did a fair amount of the statistical analysis, but her contribution was essentially just turning the crank. Given the effort she put in, I did not think it was out of place to have her as a co-author on the poster, but nor did I think it was required. I wrote the abstract and poster and asked her if she wanted to be an author and if so for any input on the abstract and poster.

Since then, I have collected a second independent data set and come up with a completely new analysis. I now feel her contribution (1/8 of the total data set and helping with a partial preliminary analysis) does not warrant authorship and I think it would be better to acknowledge her work in the acknowledgements then to add her as an author. I would discuss this with her, but she is out of the field and I cannot contact her easily. Can I drop her for the list of authors?
Most authorship questions are a gray area: she did contribute to the paper, but was it a significant intellectual contribution (which is one usual criterion), with emphasis of both significant and intellectual (or scientific)? That's for you and her to decide, taking into account the customs of your field.

From her point of view, I can see two reasons why she might be consider a rightful co-author of the paper:


If the data collection was itself part of the scientific research, i.e. if it could not have been done by an unskilled worker following instructions. If so, then her data collection was significant (and it doesn't really ).
If the conclusions drawn from the preliminary analysis were useful in tuning your final analysis, i.e. if her work helped design a better analysis method.


Though by your description it seems like she may not pass the threshold, it is true that having her as a co-author on an earlier publication (conference abstract) gives her a stronger case than otherwise. If her contribution was deemed important enough for authorship at first, and you now publish work that includes this contribution, why shouldn't she be an author? I don't think that authorship “dilutes” because other larger contributions were added…



In conclusion: you maybe have good reasons not to make her a co-author, but if she feels like fighting it, she does have valid enough arguments that it could get messy. I'd advise discussing it openly with her, but being ready to have her as co-author if she feels strongly about it.