1. Section 3.3: The Addition Rule
PROBABILITY
Section 3.3: The Addition Rule

2. Objective: To be able to understand and apply the addition rule.
“OR”: _____________________________
“AND”: ____________________________
Addition Rule: Used when only one item is being selected.
P(A or B) = P(A) + P(B) – P(A and B)
Ex. 1 Select one card from a standard deck. Find
P(Ace or Red)
P(Diamond or 4)

3. c. P(Face card or Club)
d. P(2 or 5)
Events A and B are said to be mutually exclusive if P(A and B)=0.
Ex. 2 Roll a standard die. Find
P(2 or even)
P(2 or 4)

4. Ex. 3 Using the table below, answer the following questions assuming that one person is selected. a. P(M) b. P(10) c. P(M and 10) d. P(F and 9) e. P(M or 10) f. P(F or 9) g. P(F|12) h. P(12|F) i. Are Female and 12th grader independent?
Gender/grade 9 10 11 12 M 15 55 80 60 F 20 45 50 70

5. Ex. 3 Use a Venn Diagram to answer the following questions
Ex. 3 Use a Venn Diagram to answer the following questions. Suppose there are 88 people enrolled in Statistics, 76 people enrolled in Calculus and 34 enrolled in both. Assuming there are 150 students total, answer the following questions:
Draw a Venn diagram to represent this situation.
Find P(Statistics or Calculus)
Find P(not enrolled in either course)
Find P(Statistics only)