I was wondering if someone could tell me if they think this is a typo in a course.
So, the sentence in question is,
あの人の場合はそんなことはめったにないのではないですか
The English reads: With him I believe it does not often happen.
I was thinking this was a question with the ka marker, instead of a declarative remark, but am I ignoring some grammar?
@KanaTsumoto, maybe you could help? 
I think the 「のではないですか」 at the end is basically saying “Isn’t it so?” to the proceeding statement. So a more literal way to translate it would be something like “In that person’s case, that sort of thing only rarely happens, doesn’t it?”
The information is basically the same in the translation given, but the nuance is a bit different. I’d say that the Japanese sentence expresses more of a lack of certainty on it being the case.
I could be wrong, admittedly, but that’s how I interpret it. Someone else may be able to provide a better answer. 
Yeah, it sounds like you have a similar opinion as me, with the whole “doesn’t it” tact on to your sentence. Just wondering if I were going crazy/were missing something, haha.
Hi, I’m sorry it took me a while to notice this this thread.
I couldn’t find this particular sentence in our official course (maybe it is a user generated course?), but I would say this sentence can be either a question and declarative sentence depending on sentence.
It is grammatically a question sentence, but I would say that the speaker of this has pretty much made up his mind on this. Meaning, he very much believes that “it does not often happen”. の is key in this sentence, and the speaker is trying to confirm whatever comes before のではないですか is true. This の makes what came before a noun, and in this case, makes the whole sentence a YES/NO question. This の can sometimes become ん as well.
For example…
彼のことがまだ好きなのではないのですか？ (の is making "彼のことがまだ好きだ” into a noun)
Don’t you still love him? / I thought you still loved him
Based on that interpretation, the English translation does sound right to me. Translation that @TinyCaterpillarさん gave is more accurate. (Or “in that person’s case, that sort of thing doesn’t often happen, does it?”)
Does this help??
Thank you for the explanation!