Author Archives: hangtime
Addition Rule for Complementary Events
This video covers a specific type of problem that's super-hard if you try to use the addition rule directly, but not nearly as bad if you use the complementary "1-P" trick. It's kind of like a "nor" problem, but I can't explain, just watch, you'll probably recognize it.
The Addition Rule of Probability ("OR")
This chapter explains how to use the addition rule to calculate the probability of an "or" compound event. Sometimes it's obvious, such as "Calculate the probability of rolling a 3 OR a 6", other times there's an "or" in disguise, such as "Calculate the probability of rolling an even number", which is really "2 or 4 or 6."
Compound Events
This video quickly explains what compound events are (as opposed to "simple events"), so that you can know what your professor and/or book are talking about when they mention compound events in the middle of confusing word problems.
This chapter explains how to use the addition rule to calculate the probability of an "or" compound event. Sometimes it's obvious, such as "Calculate the probability of rolling a 3 OR a 6", other times there's an "or" in disguise, such as "Calculate the probability of rolling an even number", which is really "2 or 4 or 6."
Backwards Contingency Table Problems
This video shows you how to do a very particular type of two-way table problem, where they give you a table with blanks in the middle (or you construct the table yourself as part of a word problem) and then you have to use the other values in the table -- including row and column totals -- to work "backwards" to find the missing data.
Computing Probabilities from Contingency Tables (2 Way Tables)
This video shows the easy way to compute independent probabilities, proportions, and the thing that these tables are really great for, dependent probabilities. These tables are so great, you'll find yourself drawing them even when you don't have to because it's so much safer than using formulas blindly.
What Is A Contingency Table (2 Way Table)
This video explains what contingency tables (i.e. two-way tables) are, how to fill in the totals at the end of each column in row, and how to do basic calculations from them.
These videos cover contingency tables, a.k.a. two-way tables, where things like survey results are broken out into a grid with totals at the bottom of each column and end of each row. I'll show you how to make them, how to fill them out, how to calculate proportions and probabilities from them, and how to fill in the missing spots on the table. These are so useful, you'll find yourself using them even when you don't have to!
Law of Large Numbers & 80-20 Rule
Only the Law of Large Numbers will actually be covered in your Stats class, but both it and the 80/20 rule transcend Stats, as well as space and time. You'll see both referred to in all kinds of crazy situations, so I tacked on the 80/20 rule so you can drop that in class and earn brownie points with your prof.
Tree Diagrams (Probability)
Tree diagrams for probabilities are those crazy branching messes that allow you to carefully list out all the possible outcomes (and their probabilities) of: flipping a coin three times, rolling two dice, etc. Also covered: how to use this when you're using a weighted coin!
Classical Probability Calculations
Flip three coins, how often are two flips heads? Roll two dice, what's the odds of them adding up to seven? This video covers how to do "classic" probability problems involving coin flips, dice rolls, drawing cards out of a deck, raffle tickets, and other random, equally probable outcomes.
Probability Using Empirical Method (a.k.a. Empirical Approximation)
This is like the 5th video in Stats to have the word "empirical" in the title, but that's bound to happen since "empirical" is the word that statisticians use to make "ballparking it" sound more official. Just guessing? Call it empirical, that's the ticket!
Probabilities Always Add Up To 1
The title say it all, almost. This video explains why things add up to 1, and also how to use that to your advantage when calculating probability for harder situations, like "at least one" and "complementary" situations in stats.
Probability Notation
Probability notation. Yolo! Jk. This video introduces you to a few of the symbols and weird letters that you may be confused by in your homework -- like "|" -- and tells you what they're called so that you can look up those terms in other videos.
This chapter covers most of the typical ways to estimate probability for standard situations. Also covered are some of the basic rules that make problems easier, like the fact that all the probabilities in a given situation have to add up to one, and how that helps you calculate them.
Expected Value & E-Commerce 101
How do you make a decision between two different paths that have different probabilities of success but different payoffs? How do you place a value on website visitors if most of them never buy anything? And how is this different from weighted average? Stay tuned to find out.
This chapter is short, but it covers a very important concept for business: expected value. How do you make a decision between two different paths that have different probabilities of success but different payoffs? How do you place a value on website visitors if most of them never buy anything? And how is this different from weighted average?
Odds vs Probability
In everyday life we tend to use the words "odds" and "probability" interchangeably, for example when describing the chances you'll be at your friend's birthday party. And that's mostly okay, the only time it doesn't work is when you're talking about odds on sports or horse betting.
False Positive, False Negative
A couple of terms which describe whether a test says something happened when it didn't or that it didn't when it does. Got it? Good.