Exam 10: Deduction and Induction: A Closer Look

On critically evaluating inductive arguments. Read the following arguments and carry out the instructions below. -One hundred college students from four colleges were surveyed, and 60% said they liked classical music. We conclude that approximately 60% of all college students like classical music. Does each of the following alterations strengthen or weaken the original argument? Does each leave the argument's strength unaffected? a. The colleges were all Catholic colleges. b. Actually, only ten students were surveyed. c. Actually, one thousand students were surveyed. d. All surveyed were Capricorns. e. All surveyed had grades of 3.8 or above. f. Ninety percent of those surveyed said they regularly read novels. g. Those surveyed were freshmen, sophomores, juniors, and seniors. h. Those surveyed were seniors only. i. Those surveyed were from large cities only. j. Those surveyed were from the South only. k. Those surveyed were from all regions of the country. l. All those surveyed said that they like Mars bars. m. We change the conclusion to: Exactly 60% like classical music. n. We change the conclusion to: At least 60% like classical music. o. We change the conclusion to: The majority like classical music. p. Students were surveyed at three state universities, three private liberal arts colleges, three Ivy League colleges, and three religious colleges. q. The students were actually drawn from three music conservatories: the Ace school of music, the Ajax conservatory of piano, and the Smith school of music.

Is the argument deductive (D) or inductive (I)? -The cheese has turned moldy. Mold is usually caused by organisms in the air. So the cheese likely was left exposed to the air.

An enumerative induction is deductive in nature.

The following is a weak argument: Joe has eaten lunch at the taco stand every day for sixty days straight. Tomorrow is an ordinary day. Thus, tomorrow he will probably not eat there.

Think with Socrates does not contain a section on enthymemes. However, the concept can be defined briefly. This exercise defines an enthymeme and gives students a chance to practice filling in holes in incomplete deductive arguments. An enthymeme is an argument that is missing one or more premises or a conclusion. Each of the following deductive arguments is missing either a premise or a conclusion. (Thus, each is an enthymeme.) Add a statement to each so as to turn the enthymeme into a valid argument. -If the birds are merry, it is spring … The birds are not merry.

One way to weaken an IBE is to show new facts that cannot be explained by the favored hypothesis.

If an argument is inductively strong, then it must also have all true premises.

Think with Socrates does not contain a section on enthymemes. However, the concept can be defined briefly. This exercise defines an enthymeme and gives students a chance to practice filling in holes in incomplete deductive arguments. An enthymeme is an argument that is missing one or more premises or a conclusion. Each of the following deductive arguments is missing either a premise or a conclusion. (Thus, each is an enthymeme.) Add a statement to each so as to turn the enthymeme into a valid argument. -It rains every day in the city of Sunnydale … So it will rain today.

The following is a weak argument: Joe has eaten lunch at the taco stand every day for two days straight. Thus, tomorrow he will probably eat there again.

On deductive arguments. -If the premises and conclusion are all false, the argument must be invalid.

More enthymemes. In each case, fill in the missing element (i.e., add a premise or conclusion) so as to turn the enthymeme into a valid deductive argument. -Some frogs are blue. So some frogs are young.

In an enumerative induction, generally, the more heterogeneous the cases enumerated are, the stronger the argument.

More enthymemes. In each case, fill in the missing element (i.e., add a premise or conclusion) so as to turn the enthymeme into a valid deductive argument. -All illy pies are hairy. So all illy pies are warm-blooded.

One way to weaken an analogical argument is to list relevant dissimilarities.

The following is a strong argument: Sodium burns yellow. This metal burns yellow. So this metal is very probably sodium.

In an inference to the best explanation, the less simple the hypothesis, the stronger the argument.

Organon means tool of thought.

The following is an invalid argument: Jim is under sixty. Jan is younger than Jim. So Jan is younger than sixty.

One way to strengthen an analogical argument is to make the conclusion more general, i.e., less specific.

Is the argument deductive (D) or inductive (I)? -All cats are mammals. All mammals are hairy. Therefore, certainly all cats are hairy.