Algebra 2 Note-taking Guide
Algebra 2 - Lesson 9.02 Independent Probability
Please print this out in advance, and as you are working through the lesson, fill in the information and use this as your notes.
 The goal is to have all the empty boxes checked
Use this set of arrows
to guide you through
the lesson
As you complete this lesson, please check that you can answer:
 How do we determine if two events are independent?
 How can we interpret the independent or conditional probability of two events?
 How can you construct and interpret two-way frequency tables of data?
Probability (page 1)
A family has two children.
Use the space below to record the steps/work for determining the probability that the family has two girls:
Recall that the probability is always a number between _____ and _____.
A probability greater than 1 means something is more than ________ likely.
Algebra 2 Notetaking Guide
Version 14
Florida Virtual School
Use the space below to complete examples 1 and 2 on page 1:
Example 1:
Example 2:
Independent Probabilities (page 2)
Jacob’s math teacher gave him a very strange quiz today! Thankfully it was a True/False quiz with only four
questions. Jacob just had to randomly choose true or false for each question. His teacher is so nice that everyone
who gets the first two answers correct will win a prize.
Step 1: Begin by creating the sample space
Step 2: A favorable outcome is one in which the first two answers are correct. Look at the chart and count all of the
outcomes that start with CC.
This is a key test to determine if two events are independent. In fact, there's even a formula:
If two events, A and B, are independent, then P(A ∩ B) = __________________.
Algebra 2 Notetaking Guide
Version 14
Florida Virtual School
If you divide both sides of this formula by P(B), then you will have an alternate test for independence.
If ____________ = P(A), then A and B are independent events.
Two-way Tables and Independence (page 3)
When the Titanic sank in 1912, only 713 of the 2,229 people on board survived. Some data about the survivors is
displayed below.
Crew
Passengers
Totals
Survived
215
498
713
Did not survive
698
818
1516
Totals
913
1316
2229
What is the probability of randomly selecting a crew member who survived? In other words, what is P(crew member
∩ survived)? This is also known as joint probability. Joint probability is _________________________________
__________________________________________________________________________________________.
P(crew member who survived) = ___________
Notice that the sample space includes only crew members.
Algebra 2 Notetaking Guide
Version 14
Florida Virtual School
Use the space below to test for independence between selecting a crew member and selecting a survivor:
Complete examples 1 and 2 in the space beow:
Example 1:
Example 2:
Venn Diagrams and Probabilities (page 4)
Review the Venn diagram and use the space below to determine if the
events "on medication" and "lower BP" are independent.
Use the space below to complete example 1 on page 4:
Algebra 2 Notetaking Guide
Version 14
Florida Virtual School
Conditional Probability (page 5)
So far, we have been using a very simple test to determine whether two events are independent. The important
thing to remember about independent events is that the outcome of the second event is not influenced by the
outcome of the first event.
Conditional probability is the probability that a second event occurs, given that ___________________________
___________________________________________________________________________________________.
Use the space below to complete examples 1 and 2:
Example 1:
Example 2:
Complete the 7 practice problems from page 6 on your own sheet of paper.
Finally, complete the 9.02 Assessment, Independent Probability. This is an auto-graded assignment. You will
get immediate feedback on your work.
Algebra 2 Notetaking Guide
Version 14
Florida Virtual School