Premise:
"OK, never mind."
Hypothesis: That makes more sense to me than whatever I had in mind.

it is not possible to tell

Premise:
"Not a sign of a footmark." They wandered round the deserted house."
Hypothesis: They saw many footprints when they looked around the house.

no

Premise:
"You told me yourself that he had started by studying medicine, and that he had taken his degree.""
Hypothesis: He'd gone to Harvard Medical School.
it is not possible to tell