Tag questions are something like negative questions. They
are used when someone thinks he or she knows an answer
and wants confirmation. There are two very commonly used
types of tag questions--one made from affirmative ( + )
sentences, the other made from negative ( - ) sentences:

He's from Italy, isn't he? /
He isn't from Italy, is he?

She's living in London, isn't she? /
She isn't living in London, is she?

There were at the party, weren't they? /
They weren't at the party, were they?

She speaks Estonian, doesn't she? /
She doesn't speak Estonian, does she?

He had a good time, didn't he? /
He didn't have a good time, did he?

She's lived here a long time, hasn't she? /
She hasn't lived here a long time, has she?

They'd left when you arrived, hadn't they? /
They hadn't left when you arrived, had they?

He can help us, can't he? /
He can't help us, can he?

etc.

Statements are normally said with falling intonation. Yes / No
questions are normally said with rising intonation. The intonation
of tag endings is different from both of these.

In tag questions, the tag endings (for example, isn't he?, is he?,
hadn't they?, can he? ) have two different intonations:

The intonation (falling / rising) of the tag endings is in addition
to the intonation of the statement to which the tag ending is attached.
This means that after the normal intonation (falling) of the statement,
there will be the intonation of the tag ending (falling or rising):

Question 4 is difficult,isn't it?

Question 4 is difficult, isn't it?

The falling or rising intonation of the tag endings communicates
different information.

When someone asks a tag question and the question tag has falling
intonation, the person who asks the questions is fairly sure that
the statement before the tag ending is correct. Because the person
asking the question is not 100% sure, however, he or she still
wants confirmation.

Example:

I think a question is difficult and want to know if you feel the
same way, so I say

Q: Question 4 is difficult, isn't it?
A: Yes, it's difficult. / No, it isn't difficult. / I don't know.

Q: Question 4 isn't difficult, is it?
A: Yes, it's difficult. / No, it isn't difficult. / I don't know.

When someone asks a tag question and the tag has rising
intonation, the person who asks the question is much less sure
that the statement before the tag ending is correct. However,
he or she still wants confirmation:

Example:

I think I have the answer for question 4 but am not very sure.
I want to see if you agree with me (or if you will tell me what
the answer is), so I say

Q: Question 4 is difficult, isn't it?
A: Yes, it's difficult. / No, it isn't difficult. / I don't know.

Q: Question 4 isn't difficult, is it?
A: Yes, it's difficult. / No, it isn't difficult. / I don't know.

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Remember:

The answers for tag questions are the true answers. They may
or may not be the expected answers.

Examples:

Q: Dave Sperling isn't married, is he?
A: Yes, he's married. His wife's name is Dao.

Q: Dave Sperling has two sons, doesn't he?
A: No. He has one son and one daughter.