I should think so/not

I should think not

I would naturally expect that this would happen or be true. A: "Don't worry, you won't have to pay for the additional service." B: "I should think not, seeing as I never agreed to it in the first place!"
See also: not, should, think

I should think so

I would naturally expect that this would happen or be true. A: "My manager said you can get a refund on the item." B: "I should think so—it arrived broken in two pieces!"
See also: should, think

I should think ˈso/ˈnot

(also I should think she, etc. ˈis/ˈdoes/ˈdid, etc.) used for emphasis when agreeing that something is right or correct: ‘He didn’t give the waiter a tip.’ ‘I should think not, after such bad service.’‘He finally apologized for what he said.’ ‘I should think so.’‘I’m very angry with my son.’ ‘I should think you are. He’s behaved very badly indeed.’
See also: not, should, think