AMBIGUOUS: Traveling at high speed in the dark, the ferry rammed the anchored yacht. Subsequent inspection showed it was not damaged. [COMMENT: “ferry” or “yacht?”]
NON-EXISTENT: The research was carried out in the previous semester, but they found nothing of any interest. [COMMENT: Who is “they?”]
Inexperienced authors make these kinds of errors for two reasons:
First, it is easy for the author to forget that spoken language makes available a much richer, multisensory context than does written language. From this broader context, it is usually possible for the listener to supply the proper antecedent reference to a pronoun by virtue of sharing the same context as the speaker. How many times have you felt it necessary, in spoken language, to ask a speaker for the reference to an uttered pronoun? In other words, while you are writing, you know perfectly well what the antecedents of your pronouns are as they are in your head, but your reader does not--unless you make these antecedents available in a very clear way.
Second, hundreds of students, whenever I have asked, tell me that they simply have not checked their work for this type of problem prior to submission. There is an obvious answer, of course. However, with fair ease, you can also determine whether you are prone in the first place to causing your academic readers such annoyance and frustration. Run a search for "it." You will find many. Pick any ten and examine them for this particular pronoun problem. You should find zero. If you find such errors, repeat the process with other pronouns, such as "their" or "which." In just a few minutes, you will know whether you have the pronoun abuse syndrome.
I know it is time consuming and boring to be mindful of pronoun references when concentrating on the profundities and logic of a thesis or dissertation. Think of it this way, however. When your review committee encounters ambiguous and non-existent pronoun references, some members will interpret these as a lack of respect for the standards of scholarship, and this is not good for you. Also bear in mind that if you make the effort to catch yourself on these types of errors before they happen, you can eliminate them altogether.
Twenty-five percent of the dissertations that I review do not reveal a single instance of pronoun abuse.