Z-Score As Measure of Unusualness
There are lots of ways to determine outliers, but z-score introduces yet another category altogether: usual vs unusual. It's kind of in the middle between being "usual" and being an "outlier".
Author Archives: hangtime
Z-Score Rule For Outliers
In stats they give you lots of different criteria for when a data point or measurement is "out there" enough to ignore (I meant "to call it an outlier so it's okay to ignore it"). This video considers yet another: z-scores!
Calculating Z-Score
This video covers how to calculate z-score in a few different situations. Sometimes you're given a whole list of numbers, while other times you get a word problem that tells you the mean and standard deviation and asks you to find the z-score of a particular data point.
This chapter covers everything you'll need to calculate, understand, and answer questions about z-score, a.k.a. "standard score", a.k.a. "z-value".
Coefficient of Variation
Coefficients of variation are at least mentioned in most stats books, but it's a coin toss as to whether your professor expects you to know them. If it showed up in your homework or notes, this video is for you, though it's not exactly the hardest concept you're going to see in this class.
Bias of Standard Deviation vs Variance
No matter if you're in the easiest Statistics class ever, or the hardest, your professor probably expects you to know that sample standard deviation is a "biased" estimator, whereas sample variance is an "unbiased" estimator which "targets" population variance. But what the heck does that mean? Yeah, stick around.
Standard Deviation On Your Calculator
Calculators are awesome for stats. This video shows you how to get those key stats -- including standard deviation for samples and populations -- as quickly as possible, and also making sure you grab the right one!
Standard Deviation of Samples vs Population
This video covers how to find standard deviation for population and samples, and it also gets into the differences between the formulas. Why is there an n-1 in the denominator of one formula but N in the other?
Estimating Standard Deviation via Range Rule of Thumb
This is a very specific method that not all stats classes cover. But if yours does, this video lays out the concept and shows you how to work the problems forwards and backwards.
Range
Basically just the difference between the largest and smallest value in the data set, range in statistics class is the same as it was in middle school.
This chapter covers all those numbers that can describe how spread out or narrow a distribution is: standard deviation, variance and range. It also covers a few of the less concrete ways to estimate those measures when data is incomplete, such as using the range rule of thumb to estimate standard deviation. And with each statistic covered, I show you how to find it on your calculator, and how the numbers are different for samples vs populations.
This chapter covers a couple of vocab words that you'll be expected to know for your statistics class. Will they be on the test? Depends on your teacher, though almost everyone is supposed to know that standard deviation is biased, whatever that means.
Resistant vs Biased Estimators
This video covers a couple of vocab words that you'll be expected to know for your statistics class. Will they be on the test? Depends on your teacher, though almost everyone is supposed to know that standard deviation is biased, whatever that means.
Calculating Median From Frequency Table
Another fun frequency table problem type: being asked to find the median when you don't have anything to go from other than a frequency table.
Calculating Mean From Frequency Table
This is a type of problem that's specific to Statistics class: being asked to find the mean of a data set when you don't actually have the data set, just a table with ranges on it. No problem, it's a straightforward step-by-step process to make this calculation, so let's get started!
Midrange vs Trimmed Mean
These are a couple of fun measures that not every class covers, but which are actually kind of useful in real world situations. Once you know what midrange and trimmed means are, you'll start recognizing them when you see statistics on the internet and realize what games they're playing.
Mode
I wish I could say that mode is different in Stats class than it was back in middle school. Nope! Although they do introduce a couple new terms -- bimodal and multi-modal -- so that's fun.
Median
You probably think you know all there is to know about median, but this being Stats class, there's so much more! This video covers the old-school median you know, as well as why it's a "resistant" measure of center. Good stuff!
Mean & Median on your Stats Calculator
This video shows you how to enter statistics data into your calculator and then how to get the stats you want out. It's super-easy, so don't be intimidated by all those buttons and menus!
Arithmetic Mean (a.k.a. Average)
This video explains the difference between the formula for mean that you learned in elementary school -- sum divided by number of items -- and the crazy Stats version of the formula that has Greek symbols and craziness in it. And why is there a different version of the formula for samples and population?