Jeffrey,
Sometimes situations require looking at the consequences. If a manager or another professional without deep knowledge in your area wants an answer, you can phrase it in likelihoods (what is your estimated chance of outcome 1 vs. 2) and consequences (what is the outcome for each of the choices in terms of schedule, expense, or later failure).
An old saw is, "Technology is dominated by two groups, those who understand what they do not manage, and those who manage what they do not understand." If you give those who don't understand your best data on outcomes and consequences, they have the best chance of making good decisions. And sometimes, you don't have the data, and it either is not available or will cost a lot to get - that is also an acceptable answer, because by analyzing the consequences of what happens if you proceed without it, the managers also get another choice.
One other instance of Y vs. N is when one is testifying as an expert witness in a legal proceeding. The lawyers will often try to get you to respond to an answer with Yes or No. In the case where one has been accepted as an expert, it means that your opinion and judgement are admissible. So your answer can be, "No, but...." or "It depends on....". It's valuable in legal situations that "your" lawyer, the one for whom you are working, gets your best explanation of the fuzzy matters so that they can decide which way to go.
Paul Tibbals
How have you built confidence among your peers of other professions when answers are not always Yes or No responses.
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Jeffrey Tatum