Stat 2000: Important Probability Handouts (Supplements to my Basic Stats 2 book)

Published: Thu, 10/24/13

Do note that my midterm seminar is coming up this weekend (Oct. 26 and 27).  Click here for more details:
Did you read my tips on how to study and learn Stat 2000?  If not, here is a link to those important suggestions:
Did you read my Calculator Tips?  If not, here is a link to those important suggestions:
Did you read my Tips for Assignment 1?  If not, here is a link to those important suggestions:
Did you read my Tips for Assignment 2?  If not, here is a link to those important suggestions:
Extra Probability Help
I am surprised to see a lot of probability questions on the sample exams that are really from Stat 1000, so here is a handout from my Basic Stats 1 study book with a more thorough discussion of making two-way tables and Venn diagrams.  Those of you who have my Basic Stats 1 book, should study Lesson 5: Introduction to Probability.
Conditional Probability
Here is another handout explaining the approach to determine a conditional probability:
Conditional Probability Handout

Essentially, in conditional probability, when it says "given A" it is telling you that we know for sure that event A has occurred, so we are now only interested in outcomes that belong to A.  That becomes the "whole".  P(B|A) wants the fraction of that "whole" that also belongs to B.

For example, if you look at my question 18 in the probability handout from my Basic Stats 1 Probability Lesson above, I could add a part (d) that asks, "What is the probability someone is a basketball fan if they are a hockey fan?"  Any probability question that asks, what is the probability of B if event A has occurred, you are doing conditional probability.

We want P(B|H).  I first look through my Venn diagram and find all the bits that belong to H, since we know for sure the person is a hockey fan. There are four bits in the H circle so I add those bits up: 33 + 31 + 8 + 5 = 77%.  Now, I gather all the bits in that H circle that represent people who are also basketball fans.  There are two bits: 8 + 5 = 13%.  Thus, the probability a person is a basketball fan if they are a hockey fan is 13%/77% or .13/.77 = .1688.

Here is a couple of extra conditional probability questions I have added to question 4 in my Probability Lesson handout above:

Here is a couple of extra conditional probability questions I have added to question 16 in my Probability Lesson handout above:
Please note that I will discuss Probability and Conditional Probability at the seminar this Sunday, Oct. 27.  You should bring copies of these handouts with you to the seminar if you would like to follow along as I go through these concepts.