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Statbag is the personal website of Worth Swearingen, a high school math teacher

Resources for AP Statistics, 2009-2010 · May 29, 01:01 PM

Welcome to AP Statistics. Like many AP classes at Aiken High, AP Statistics includes some summer work. You’ll read a book and you’ll complete a few short assignments. The assignments are designed to refresh your memory about statistics you already know.

What’s missing?

I have omitted some basic practice with probability. You have other important things to do this summer instead. If probability is already an interest of yours, you may want to read up, but I don’t expect it.

Short assignments

Once you finish the assignments listed below, I will expect you to be able to do the following:

And that’s all. Put another way, you should know when to use and how to hand prepare these graphs: pie charts, bar graphs, histograms, stem-and-leaf plots, frequency polygons, line plots and dotplots. (You can skip box-and-whisker plots, for now). Many of these are graphs you started drawing in elementary school. The rest of the material assigned is context. When you come back to school, you should be ready to draw any of these graphs with data I provide.

  1. Introduction: read and complete the self-test exercises on the following pages.
    1. (5 minutes) What are statistics?.
    2. (5 minutes) The importance of statistics
    3. (10 minutes) Types of variables. See my footnote1.
    4. (30 minutes) (Optional) Against All Odds, Episode 1. Some of you may want to watch this show, too. We’ll watch pieces from the series throughout the year. You must register, but watching is free.
  2. Graphs: read and complete the self-test exercises on the following pages.
    1. (10 minutes) Graphing qualitative variables
    2. (1 hour or less) Graphing quantitative variables. Break this one up because it’s important. Go through all the links. (You can skip box-and-whisker plots, for now).
    3. (30 minutes) (Optional) Against All Odds, Episode 2. This website requires you to register, but watching is free. This episode illustrates histograms well.

1 I’m skipping you down to the section about quantitative and qualitative variables. You don’t need to read the material that precedes it. You should read the material that follows it, however. Also, our textbook refers to qualitative variables as categorical variables. I’ll use the term “categorical variable” much more often.

Cleaning house · May 29, 08:43 AM

I’m in the process of cleaning up the website for next year. Some files may be dead links, now.

I will be uploading files and links for AP Statistics beginning today. Click on the AP Stats link to see.

AP Stats: Scoring guidelines · May 4, 08:14 PM

Good luck!

On independence · Mar 12, 11:55 AM

We’re having a quiz in CP Stats, tomorrow. On the quiz, I’ll give you one scenario. You will need to verify that the trials are Bernoulli trials (that is, like coin flips), prepare a probability table, and use your table to state probabilities. You’ll also calculate the expected value (or mean), the variance and the standard deviation of the binomial random variable.

The question most likely to trip students up is the question of independence. Like a coin flip, the outcome of a Bernoulli trial must not depend on what’s happened prior to it. Loosely speaking, we’ve said that a coin has no memory, and it certainly does not. The outcome of the next coin flip does not depend on the 50 or 100 coin flip outcomes that came before.

We must be careful not to overstretch this analogy, though. Literally speaking, a card in a deck has no memory, either. However, outcomes may depend on what’s come before. Consider the following probability question:

If I draw 20 cards out of a deck and I do not replace them, what’s the probability that the 21st card drawn is a red card?

Hopefully, you wouldn’t claim to know the answer to this one because so many cards have been drawn out of the deck. Your answer depends on the cards previously withdrawn. If all 20 cards drawn previously were red, the probability that the 21st is red is low (6/32 or 3/16). Draw out 20 black cards and the probability of a red on the 21st draw is much higher — 13/16.

So, be prepared to determine whether too many cards (or other things, like people) are drawn out of the population. For this purpose, we’ll say that “too many” is more than 10% of the population. In the context of our card drawing problem, we cannot draw out more than 5 cards (5% of 52 is 5.2) and still treat each outcome as being independent.

AP Stats: We need structure · Mar 5, 12:41 PM

There is a lot of stuff about inference that you need to memorize. You’ll never remember it if you simply try to stuff it all in your brain and hope to find it later. Therefore, I’m adding an assignment due March 13 and every Friday (or last day of the week) thereafter when we add new inference procedures: an .

The rules

  1. The outline must be your work. I encourage you to discuss your outlines with each other and to help each other fix errors. However, with one exception I describe in the next item, the work you turn in must be yours, not your modification of another’s work.
  2. I encourage you to copy/paste your work from one procedure to the next and simply change formulas, etc. as needed. And I’ve given you a big head start by outlining 1-proportion z-procedures using the required format. This work you may use in your outline verbatim with one exception — come up with your own example scenarios.
  3. You may hand write your formulas if you want. Keep handwritten formulas with you in class so that you can show them to me on the due dates. Leave space in your typed outline so that you can add the formulas to the final version.
  4. Turn in the outlines in electronic form. Don’t waste the trees. You can send them to me via e-mail. (The e-mail link isn’t working — I’ll fix it tonight).