吗 and 吧

[Outofin]

Please tell me if my translation is correct.

Is it? 是吗？

It is, isn't? 是吧？

Isn't it? 不是吗？

It isn't, is it? 不是吧？

[doraemon]

Yes, they all look fine to me (although the English kind of started to confuse me).

[Don_Horhe]

I personally wouldn't use '不是吧' the way I'd use 'It isn't, is it?'. To my ears, '不是吧' is 'It isn't.', said with only slight uncertainty and a hybrid between a period and a question mark, while in 'It isn't, is it?' certainty and uncertainty are 50/50.

[doraemon]

I suppose you could soften the expression a bit and say 应该不是吧？But I still think 不是吧 is quite legitimate depending on the tone of the speaker's voice.

[renzhe]

To me, 不是吧 sounds like "It can't be! Really? But I think that the context matters.

Otherwise, I understand these like you do, if that helps any.