HW#1 (due September 1)

This initial homework is primarily a diagnostic tool, so it (unlike the others) will be graded for completeness rather than correctness. You can thus receive full credit simply by completing all the questions.

1. Which of the following passages contains argument?

I. I don't like Japanese cars, and I don't care what you think about them.

II. Japanese cars generally have better mileage than American cars, and are much more reliable. However, they tend to be smaller and buying one can contribute to our trade deficit.

III. You should buy a Saturn instead of a Honda, because Saturn's have a better resale value.

a. I

b. II

c. III

d. I, II, and III

(I) is essentially a refusal to give an argument for one's opinion, while (II) contains a number of facts which could be used in an argument, but no conclusion is actually claimed to follow from them.

2. Which of the following arguments valid:

I. If Jeff had something to hide, he would refuse to testify in his trial. He refused to testify, so he must have something to hide.

II. Either Peter or Mary took the car. Since Peter has been in Hong Kong all week, he couldn't have taken the car. Consequently, Mary must have taken the car.

III. When John is happy, he won't see a psychiatrist. He is seeing a psychiatrist, so he must not be happy.

a. I and II

b. I and III

c. II and III

d. I, II, and III

(I) seemed valid to many, but the argument form is an invalid one. In particular, it has the same form as the argument: If Jeff were a serial killer, he would never admit it. Jeff has never admitted to being a serial killer, so he must be one.

3. Mary graduated from Ohio State in 1992 with a double major in Sociology and Women's studies. She was a member of Amnesty international and Students for a Democratic Society. Which of the following guesses about what she is doing now seems most likely to be true?

 

a. Mary is a financial consultant.

b. Marry is a financial consultant and a feminist.

c. Mary is a financial consultant working for Amnesty International.

d. All three are equally probable.

(a) is the correct answer here because any possibility in which either (b) or (c) are true, (a) will be true as well (you can't be a financial consultant and a feminist without being a financial consultant) while there are possibilities where (a) is true while (b) and (c) are false.

4. If the odds of the Indians winning the World Series are 1 to 4, what is the probability of their winning the World Series.

a. 14%

b. 0.25

c. 25%

d. 20%

The answer is (d) because if the odds of something happening are n to m, the chance of that things happening are not n/m, but rather n/(n+m).

5. Which of the following claims is true:

a. Being a mammal is a necessary condition for being a dog.

b. Being a mammal is a sufficient condition for being a dog.

c. Being a mammal is both a necessary and a sufficient condition for being a dog.

d. Being a mammal is neither a necessary nor a sufficient condition for being a dog.

Being a mammal is a necessary condition for being a dog, because (since all dogs are mammals), you can't be a dog without being a mammal. Being a mammal is not a sufficient condition for being a dog because there are lot of things (cats, mice, humans) that are mammals but not dogs.