"How do first-generation students experience advising, and does it affect persistence?" asks about experience and about an effect. Those call for different designs, different data, and different standards of evidence.
When a committee member writes "unclear aim" in the margin, a compound question is frequently the cause. The sentence reads smoothly, so the writer does not see the seam. The reader does, because the reader has to picture the study that would answer it and cannot.
Test a question by counting its verbs and its nouns of interest. Two verbs ("experience" and "affect") usually mean two questions. Two outcomes in one sentence ("engagement and achievement") usually mean two as well.
Splitting the question is the first step. Deciding which question the dissertation will answer is the second, and it is the harder one. A study that tries to answer both usually answers neither well, because the sample, instruments, and analysis suited to one are poorly suited to the other. If both questions matter to your field, one can become the dissertation and the other a stated direction for future research.
Two practical checks follow. First, write the study you would run for each question separately. If the two studies share nothing, the question was compound. Second, read your research questions against your significance statement. If the significance statement promises more than the surviving question can deliver, trim the statement before the committee does.
After splitting, check the downstream chapters. The literature review, the instruments, and the analysis plan all inherited the compound question. Each needs a pass for language that still points to the second half.
This is practitioner guidance drawn from coaching doctoral students in education, not a research finding.
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