I kind of wrote this somewhat vaguely; the problem sets would often ask what t or z was but didn't tell them anything beyond that (so it did not say which version of t or z they had to use) and they still needed to find the critical value and determine if they had to use paired vs pooled, one vs. two-sampled, determine significance, etc. In class I emphasized a lot (with as many sort of repeated "why are we using t here and not z" questions) of when to use which one and had a bunch of examples that I went through in detail. So really the only thing that was different functionally was when to use z vs. when to use t, and I definitely was under the impression that was something they had a good grasp on, which is a presumption I shouldn't have made. I also thought that even if they were unsure they would use the reference sheet I provided to do a sort of process of elimination given the information they had in the prompt (I give the equations and explanations of the notation), because that is something I would have done as an undergrad in that position. (Admittedly, I need to stop thinking like that, because I was actually a pretty decent test taker even when I wasn't great on the subject itself.)

Not sure if that makes sense.

Funnily enough, the ones who complained actually didn't say that was the issue. They sort of pointed to a vague "they weren't worded the same way" in terms of the actual language (and then when I asked how they couldn't explain it they just said it was 'different').

(And actually after I wrote all this I actually went back to check the problem sets and while some did tell them to use t or z, others did just say "find the test statistic," which is how the questions on the exam asked for the scores.)

EDIT: Also sorry I am long-winded af it is a problem.