She doesn’t want a real investigation, does she?

[diamondcutter]

1. A: She doesn’t want a real investigation, does she?
B: I think not. / I think so.

I think not. = I don’t think so. = I don’t think she wants a real investigation. = I think she doesn’t want a real investigation.
I think so. = I think she wants a real investigation.

2. A: She wants a real investigation, doesn’t she?
B: I think not. / I think so.

I think not. = I don’t think so. = I don’t think she wants a real investigation. = I think she doesn’t want a real investigation.
I think so. = I think she wants a real investigation.

Are there any mistakes above?

 

[bhaisahab]

They are all OK.

 

[Roman55]

I am not a teacher.

Yes, they're OK grammatically but I find 'I think so' an unnatural and ambiguous answer in case 1.

I wouldn't be sure when reading 'I think so' whether the person thinks that she does or doesn't want a real investigation. I would be equally confused if the answer were 'Yes'.

In the spoken language, voice inflection might dispel the ambiguity, but it would be clearer to say 'I think she does'.