PSY 555 Homework 8

Chapter 5: #2,3,5,9

1. State the additive and the multiplicative law of probability and give an example of each.

2. Describe joint probability and conditional probability and give an example of each.

3. With regard to probability, how are discrete and continuous variables treated differently?

4. Volunteers coming into a blood center are such that 1 in 5 have O+ blood, 1 in 21 have O- blood, 1 in 3 have A+ blood, and 1 in 13 have A- blood. The name of one person who previously donated blood is randomly selected from the records of the center. What is the probability that the person selected has:

a. O+ blood?

b. Type O blood?

c. Type A blood?

d. Neither Type A nor Type O blood?

e. Type A+ and O+ blood?

f. Why is the probability in "e" what it is?

5. A large group of people are examined for the presence of two physical traits. It is thought that 40% of the people possess trait A alone, 25% possess trait B alone, 8% possess both traits, and the remainder possess neither trait. For each person chosen at random from this group, find the probability that:

a. the person has neither trait.

b. the person has at least one of the traits.

c. the person has trait B.

d. the person has both traits, given that he has trait A.