Download Lesson 2: Probability Rules

AP Statistics
Peterson
Lesson 2: Chapter 5 – Probability Rules (Take Home Notes + Assignment)
Probability Vocabulary
Sample Space S:
Probability Model:
Event:
Mutually Exclusive (disjoint):
Question #1:
Imagine tossing a fair coin 3 times.
a) What is the sample space for this chance process?
b) What is the assignment of probabilities to outcomes in this sample space?
To find the probability that an event A happens, we rely on some basic probability rules:
Probability Rules
1.
2.
3.
4.
5.
AP Statistics
Peterson
Two-Way Tables
Example
Students in a college statistics class wanted to find out how common it is for young adults to have their ears
pierced. They recorded the data on two variables – gender and whether the student had a pierced ear – for all
195 people in the class. The two way table shows the data:
Pierced Ears?
Gender
Male
Female
Yes
17
90
No
82
6
Total
99
96
Total
107
88
195
Suppose we choose a student from the class at random. Find the probability that the student:
a) Has pierced ears
b) Is a male with pierced ears
c) Is male or has pierced ears
GENERAL ADDITION RULE for TWO EVENTS:
AP Statistics
Peterson
Venn Diagrams
Label the following diagrams, using proper symbols and notation:
Event A and it’s complement AC
Mutually exclusive (disjoint) events A and B
Intersection of events A and B
Union of events A and B
Question #2
The two-way table below describes the members of the U.S Senate in a recent year
Democrats
Republicans
Male
47
36
Female
13
4
a) Construct a Venn-Diagram that models the chance process using events R: is a Republican, and F: is a
female
b) Find P(R U F). Interpret this value in context.
c) Find P(RC Ո FC). Interpret this value in context.