Author Archives: hangtime

Z-Scores In Reverse-Calculating Cutoffs From A Probability

Once you already know how to do the crazy z-score table problems in the previous video, this video covers a particularly over-the-top version of those problems: instead of giving you a cutoff x and asking you for the percentage above or below that value, they give you a percentile and ask for the cutoff x value. Pretty crazy.

This video appears on the page: Calculating Probability Using Z-Score & Normal Distribution

How To Read A Z-Score Table

This video shows you how to use those z-score tables which give you the "area to the left" of a z-value. They can be a bit confusing when you first see them, plus there's some wacky stuff going on around zero.

This video appears on the page: Calculating Probability Using Z-Score & Normal Distribution

How To Spot Z-Score Table Problems

Before you can do a z-score table problem, you've got to know what they look like. So this video gives you everything you'll need to know to spot these puppies on the test, from the easy ones to the most crazy one I've ever seen.

This video appears on the page: Calculating Probability Using Z-Score & Normal Distribution

The Normal Distribution: Calculating Probability Using Z-Score:
Calculating Z-Score
How To Spot Z-Score Table Problems
How To Read A Z-Score Table
How To Use Z-Score Table To Calculate Probability & Proportion
Z-Scores In Reverse-Calculating Cutoffs From A Probability
Z-Score Table Calculations On Your Calculator

These videos cover all those crazy word problems where they give you the mean and standard deviation of a population, then ask you what percentage of that population is shorter or taller or heavier or lighter than some cutoff value. That's what the normal distribution is all about. And of course we'll also cover how to do all this on your calculator.

Part of the course(s): Statistics

Continuous vs Discrete Probability Histograms

This video is really short, just to clear up a few of the most common questions about discrete and continuous probability histograms (graphs).

This video appears on the page: How to Read Continuous Distribution Curves (Density Curves)

Uniform Probability Distributions (Continuous)

We've seen uniform distributions before, in their discrete form, but now we'll get their continuous form, which can be a bit more confusing than a roll of the dice. A common example: if a bus arrives every 10 minutes, your wait time is equally likely to be any random time between zero and 10 minutes.

This video appears on the page: How to Read Continuous Distribution Curves (Density Curves)

How to Read Continuous Distribution Curves (Density Curves)

This video introduces the basics of what you're supposed to know about every continuous distribution curve: How to interpret area as probability, the one thing that all continuous distributions have in common, and the common confusion that can come from looking at the y-coordinate as a probability.

This video appears on the page: How to Read Continuous Distribution Curves (Density Curves)

How to Read Continuous Distribution Curves (Density Curves):
How to Read Continuous Distribution Curves (Density Curves)
Uniform Probability Distributions (Continuous)
Continuous vs Discrete Probability Histograms

This chapter introduces the basics of continuous probability distributions, also known as density curves, and explains the difference between them and the discrete distributions you've been using up to this point in Stats class.

Part of the course(s): Statistics

Examples Using Poisson Approximation of Binomial Distribution

This video covers the nitty gritty. Thankfully these problems are a lot easier to execute than they sound; once you figure out which problems to use this method on, the plugging-and-chugging isn't actually all that bad.

This video appears on the page: Poisson Approximation of Binomial Distribution

When To Use Poisson Approximation of Binomial Distribution

This video covers the most important thing you need to know about these obscure problems: how to tell the difference between one of these vs a normal binomial probability problem. Also covered are the rules/technicalities you should know.

This video appears on the page: Poisson Approximation of Binomial Distribution

Poisson Approximation of Binomial Distribution:
When To Use Poisson Approximation of Binomial Distribution
Examples Using Poisson Approximation of Binomial Distribution

This topic isn't covered by many Stats profs, but if yours covers it, you'll want to see these videos. I cover how to do them, as well as how to spot them on your test.

Part of the course(s): Statistics

Usual vs Unusual Events for Poisson Distributions

This video covers a very specific type or problem that is used by every book and prof: determining whether a number of events is "unusual" -- either high or low -- using the Range Rule of Thumb.

This video appears on the page: Poisson Distributions

Standard Deviation & Variance of Poisson Distribution

This video just covers the basic formulas you have to use to calculate the variance and standard deviation for a Poisson distribution.

This video appears on the page: Poisson Distributions

Calculating Probability Using Poisson Distribution

Now that we laid the groundwork for Poisson problems in the previous videos, it's time to actually solve a few problems! Whenever you've got a problem involving the number of times something will happen over an hour or a week or any other period of time, Poisson is the formula for you.

This video appears on the page: Poisson Distributions

The Rules For Poisson Distributions

This video quickly lays out the "mathy" technicalities of when you are allowed to use Poisson formula to solve word problems that look like they should be Poisson problems. Do you really need to know these? Probably not. Will they be on a multiple choice test? Maybe.

This video appears on the page: Poisson Distributions

How To Tell Difference Between Poisson vs Binomial Problems

These two types of problems are always taught in the same chapter, so they can get confusing for that reason, but this video explains lays out exactly how to know which formula to use on which problem.

This video appears on the page: Poisson Distributions

When To Use Poisson Distributions

Before you start randomly plugging stuff into formulas, it's a good idea to know which problems you should be using the formulas for! So this video lays out the trademark signs of a Poisson problem, so you don't just think of it as the "other" binomial probability theorem.

This video appears on the page: Poisson Distributions

Poisson Probability Distributions:
When To Use Poisson Distributions
How To Tell Difference Between Poisson vs Binomial Problems
The Rules For Poisson Distributions
Calculating Probability Using Poisson Distribution
Standard Deviation & Variance of Poisson Distribution
Usual vs Unusual Events for Poisson Distributions

These videos cover everything you'll need to know to do Poisson probability distribution problems -- problems that deal with events in a time period, like how many customers walk into a Starbucks between 10:00 and 11:00 each morning. Also covered is how to tell these apart from binomial problems.

Part of the course(s): Statistics

Usual vs Unusual Events For Binomial Distribution

This is a common type of question which every book covers, every professor will ask at one point on a quiz or test, so definitely worth reviewing.

This video appears on the page: Binomial Probability Calculations

Variance & Standard Deviation of Binomial Distributions

This video covers the formulas for variance and standard deviation for a binomial distribution -- using nothing more than n, p, and q -- so that you can plug it into those "unusual value" problems.

This video appears on the page: Binomial Probability Calculations