A couple of years ago, a colleague and I collaborated on a research report where we each collected a different set of data for our report. At the time, I conducted a set of interviews with one group of participants (school teachers) and my colleague conducted interviews with a completely different set (college profs). We each analyzed our data independently and wrote our own part of the discussion section pertaining to the data set we collected. The result was a research report that we presented at a conference and which we never published in a journal. My question is: would it be ethical to write a new paper based on the data I collected and excluding my colleague's sdata? Of course, I would have to modify the whole paper starting with the research questions to the literature review and other parts of the paper as well. In other words, I would write a 100% original paper using data collected for a different study. What is your take on this? I appreciate the responses!
Presumably you designed the experiment together. That makes it a joint work. The best way forward is to find a way to work with your co-author on the paper.
In an extreme case, but ethical, you could write the paper yourself, list both of you as authors, and just get the other person to approve of it. More work for you, of course, but it avoids all the pitfalls.
But, perhaps in seeing a draft, they will decide to contribute more.
If you are willing to state a research question that depends only on your own ideas, re-define the methodology, and then re-gather data to test it is another way forward, that might only require acknowledgement of the other person's early contribution. But the existing data is tainted at this point.
It might not be ethical. If you and your colleague discussed the questionnaire design and the methods you would use to analyze the data then even though you are using only your own data this new work is not yours alone.
If you are simply reusing your data to try to address a different question it is probably OK.
You should discuss how to go forward with your colleague. Perhaps just an appropriate acknowledgment in a discussion of the history of the previous project would do. Perhaps coauthorship is really called for.