Academic Poll: Exam Philosophy [Uncertain Principles]

I'm spending a good chunk of the morning grading the exam that I gave yesterday, so here's a poll on what you might call exam philosophy. Our classes are small, so the bulk of our exams are free-response problems, and we tend to break those problems into sub-parts (1a, 1b, 1c, etc.). There are two approaches to writing these questions that I have seen: one is to use the sub-parts to break a single problem into steps, thus leading students through the question; the other is to write questions where the sub-parts are independent, so that a student who has no clue how to answer part a can still go on to parts b-f without needing the answer from a.

There are reasonable arguments for each of these, so I'm interested to hear what other people think:

Exam questions with multiple parts should be:online survey

The exam in question is about classical E&M, so you can only choose one answer, not a superposition of multiple answers.
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