Author Archives: hangtime
Deceptive & Misleading Graphing Technique
Calling it "technique" makes it sound like deceiving people is something you should learn how to do in stats class. But if you can't do it, you won't be able to spot it either, and this is probably going to be on at least one test question about graphing!
Frequency Polygons
Very similar to a line graph, these are actually a type of graph that you come across a lot on the internet if you ever read articles about political polls, economic data, health news, etc.
Pareto Charts
Pareto charts are just a subset of bar graphs: same great categorical data, arranged in a different order for maximum readability!
Bar Graphs
You've been seeing these since early grade school, and not much has changed in all those years except that... Well, not much has changed.
Stemplots (Stem-and-Leaf Plots)
These are funky because it's not completely obvious why they even exist. Like who cooked them up? I'm sure they're very useful in some particular field of science or engineering, but not in anything I've ever seen, and you can't do them on a calculator, so bummer.
This chapter covers a bunch of the quick plots that some classes cover but which you'll never see much after the first chapter of the book. Many of them are ones you've seen since grade school under other names, others will just have you scratching your head as to why they even exist.
Interpreting Scatterplots
This video introduces you to the basics of scatter plots when you're looking at them on a calculator: linear, non-linear, positive and negative correlations, etc.
Scatterplots (a.k.a. Scatter Plots) On Your Calculator
As the name implies, this video is indeed about scatter plots on your calculator, and a couple of common mistakes that can really trip you up.
Scatterplots usually come up again in later chapters of statistics class, when it's time to analyze them for correlation constants, curve fits, etc. In these videos we'll just introduce what a scatter plot is, and show you how to graph one on your calculator.
Interpreting Normal Quantile Plots
Once you've got yourself a normal quantile graph, the next thing you've got to do is interpret the darn thing! I would argue that the first thing to do is look at the histogram instead, but if you can't do that (like a no-calculator quiz), this video shows you what these plots mean, and the common patterns to look out for.
Normal Quantile Plots On Calculator
In most stats classes, the only way you'll ever have to make a normal quantile graph is on your calculator. Doing them by hand is just silly! So this video explains how to do that, as well as a couple of common errors to avoid (hint: stat-fit rules!).
Normal quantile graphs really only have one use: they tell you if your data set is normally distributed or not. This chapter covers how to make them on your calculator, how to interpret them, and also some patterns you can learn to recognize that indicate in what way your data isn't normal.
No matter which calculator you use, these videos are going to save your bacon, and/or set you off on the right foot. Especially awesome is the discussion of how to set your window, because in no other area of math are the TI calculators so ridiculous: "Why the heck is my calculator displaying a bar graph where each bar has a width of 1.66666666666663?" You'll never know why, but with these videos it won't matter, because I'll show you how to set up your window to never confuse you again (and do other stats stuff good to).
Common Calculator Mistakes
This video focuses on stats specifically, but some of the errors are applicable for other math classes as well: setting the window size correctly, how to deal with syntax errors and other uninformative error screens, not mixing up your minus signs.
Calculator Window & Zoom Settings
You may not realize this, but the "window" and "zoom" buttons are the most misunderstood buttons on your calculator, and they lead to 90% of the errors and frustration that students have with TI-83 & TI-84 calculators. This video shows you how to nail them, which is especially important in statistics since stats graphs seem to have the most confusing settings: Xscl, Yscl, etc.
Entering Stats Data Into Calculator
This video shows you how to enter statistics data -- such as that long series of numbers given to you in a typical stats problem -- into your TI-83 or TI-84 calculator's tables so that you can take advantage of its graphing and data-crunching abilities.
Overview of Stats On Calculators
This video covers all the menus and data-entry button-presses you'll need to handle basic statistics calculations and graphs on your calculator. Later videos cover the minutia of setting the right window, entering data, and avoiding common mistakes.
Histograms On Your Calculator
Now that you're already a master of drawing histograms by hand, we'll show you how you'll actually do them: on a calculator.
Graphing Frequency Histograms (Dot Plots)
Before you can do one of these histograms by hand, you first have to start with a frequency table, so if you haven't already watched that video, do so now!. Then the histogram is easy, just be sure to use class boundaries properly.