In a non-deductive argument, the conclusion 'goes beyond' the premises. Inferences in which the conclusion amplifies the premises is sometimes called ampliative inference. An argument is inductively strong if and only if it is improbable that its conclusion is false while its premises are true. The degree of strength of an inductive argument may be measured by the probability of that the conclusion is true given that all the premises are true. The probability of the conclusion of a deductively valid argument given the premises is one, so deductively valid arguments may be thought of as the limiting case of a strong inductive arguments.
Ampliative arguments have an inductive strength less than one.
The probability of the conclusion given the premises can change from person to person, as it depends on the stock of relevant knowledge possessed by a given person at a given time. There are multi-celled organisms living on Mars. Therefore, there is intelligent life on Mars. There are multi-celled organisms living on Mars. Therefore, there are single-celled organisms living on Mars.