An example of deductive reasoning is: "All oranges are fruit, all fruits grow on trees, therefore all oranges grow on trees." A mathematical example of deductive reasoning is: "If one equals two and two equals three, then one equals three."
With deductive reasoning, a researcher moves from a theory on a topic to more specific hypotheses that can be tested using collected observations. A deductive argument is valid when the conclusion logically follows from the premises. A deductive argument is sound when it is valid and the premises are all true. An example of sound deductive reasoning is: "Johnny is a bachelor, all bachelors are single, therefore Johnny is single." An example of invalid deductive reasoning is: "All flight attendants can swim, Ralph knows how to swim, therefore Ralph is a flight attendant."