Please **check your mail frequently.** (If you’ve
set up forwarding to another address, you still have to
**log in to your TC3 email at least once a semester** or the
account will go inactive.)

- 14 May: Grades have been posted
- 29 April: Chapter 12
- 8 April: Interpreting a Two-Tailed Test
- 31 March: Triage
- 26 March: Peremptory challenges
- 18 March: Homework
- 16 March: Midterm grades posted
- 4 March: Homework
- 3 March: Snow!
- 14 Feb: How to Work a Math Problem
- 14 Feb: Advice for the Sleep Lab
- 10 Feb: Boxplot without the Program
- 7 Feb: Suggestions
- 3 Feb: Early-Bird Labs, and Take-Home Quiz
- 23 Jan: Textbook and Calculator Requirement
- 5 Jan: Calculator requirement

Greetings, statistics buffs!

Grades have been posted, and you can pick them up in myTC3/myInfo. If you’d like a detailed computation of your grade, including your score on the final exam, drop me a line from your TC3 email account.

Have a great summer!

Greetings, statistics buffs!

Just so we’re all clear: Chapter 12 will be on the final exam. There won’t be a quiz on Chapter 12, but homework will be checked.

Greetings, statistics buffs!

Let me give you another explanation for last night’s example.

Recap of the problem:

In June 2013, Pew Research found that 45% of Americans felt X.
In October 2013, a new random poll of 1504 Americans found that 737
felt X. At α = 0.01, did the proportion of Americans
that felt X change between June and October?

H_{1} was p ≠ 0.45; we computed
p-value = 0.0018 and p̂ = 0.49.
p-value < α, so we
accepted H_{1} and declared that the proportion of Americans that felt X
did change.

But then we went further, saying that the change was an
increase not a decrease, because the sample proportion
p̂ = 0.49 was greater not less than the 0.45 in
H_{0}.

If that seems like it came out of nowhere, this may help. Compute the 99% confidence interval (99% because 1−α = 1−0.01 = 0.99), and you get (.45682, .52383). Notice that the whole interval is above 0.45, so you’re 99% confident that the population proportion in October was above 0.45.

That confidence interval is the link that justifies “after a two-tailed test finds p < α, you can further say that the direction of change matches the direction of the sample.”

Greetings, statistics buffs!

The “Triage” page that I mentioned is at

http://BrownMath.com/stat/castriag.htm

You can get to it from the main textbook page: In the reference section click Inferential Statistics: Basic Cases, then above the table on that page you’ll see a link for Triage: Which Inferential Stats Case Should I Use?

Greetings, statistics buffs!

In class Tuesday, the question came up about gender bias in
peremptory challenges. A little googling turned up this:

http://law.jrank.org/pages/7925/Jury-SHOULD-PEREMPTORY-CHALLENGE-BE-ABOLISHED.html

It cites the 1986 case Batson v. Kennedy, in which
the Supreme Court ruled that peremptory challenges are not to be based
on race or gender.

Other forms of discrimination are still allowed. “A peremptory challenge based on a juror's religion, age, income, occupation, or political affiliation cannot be questioned as long as it is not a pretext for concealing race or gender bias.”

Greetings, statistics buffs!

Just so there’s no misunderstanding — to get credit for homework, you need to show your work. Just writing down an answer doesn’t count, if the question involves computation.

I don’t check your homework carefully, since I assume you’ve checked it yourself, but do show all the computations that you perform.

Greetings, statistics buffs!

Midterm grades have been posted. I’ll have a detailed grade computation for you at our next class, but if you’d like it sooner just send me an email request from your TC3 account.

Greetings, statistics buffs!

Both Chapter 5 and Chapter 6 homework will be checked next Tuesday. If you can arrive before 6:15, that would be very helpful!

Greetings, statistics buffs!

TC3 is closed because of the weather. There will be no quiz on Chapter 5. Study Chapter 6 on your own, and there will be a quiz next time on Chapter 6.

The Shoe-Size Lab will be due next time, and will not be accepted after then. You can earn the early-bird bonus on the Probability Lab by turning it in next time, but the actual due date remains 24 March. (There’s no class on St. Patrick’s Day.) Everything you need for the Probability Lab was covered in Chapter 5.

Two bits of advice for both labs: read and follow directions, and make sure you answer the actual questions.

If you want to know how you did on the Chapter 4 quiz, or on any lab you turned in last time, please email me from your TC3 account. As always, statistics questions are welcome from any account.

Greetings, statistics buffs!

Some helpful tips are on a page called, oddly enough, How to Work a Math Problem. You can find it from the main Web page under More Info » General Math / Study Tips.

Greetings, statistics buffs!

The Sleep Lab wants some of the same kinds of graphs you made on the quiz. There were a couple of common trouble spots, especially the labeling of the horizontal axis of a histogram.

I’ve added several common mistakes to the posted quiz solutions. Take a look — if you did any of the same things on the Sleep Lab, now’s the time to fix it!

By the way, here are the results of the quiz: N = 16, Median = 12.0, μ = 12.0, σ = 2.0. There were 2 A’s and 2 F’s.

Greetings, statistics buffs!

If you don’t have the MATH200A program, you can still make a box-whisker diagram — it’s just a little more work.

On the main site page, type `box-whisker`

in the
search window. Or just go to
http://BrownMath.com/ti83/boxplot.htm
directly.

Greetings, statistics buffs!

Just a reminder: You may want to get started on your Sleep Lab by collecting the data, and maybe even doing the first graph. Please review systematic samples in Chapter 1.

How to Take a Math Test or Quiz gives some
helpful tips. You can get to it in the menu under *More
Info* » *General Math / Study Tips*.

Think about joining a classmate as study buddies. Getting together once a week to talk through the lesson can give you a big boost.

Greetings, statistics buffs!

It’s the Shoe-Size Lab that will carry the early-bird bonus, not the Sleep Lab. I’ll have a corrected schedule for you tonight.

If for any reason you’re missing class tonight, make sure to email me your answers to the take-home quiz before 6:30 PM for credit — not the questions, just the numbered answers.

Greetings, statistics buffs!

The textbook is free and readable on line, or you can print
it:

http://www.tc3.edu/instruct/sbrown/swt/

You will need a specific calculator, one of these four:

- TI-83 Plus
- TI-83 Silver
- TI-84 Plus
- TI-84 Silver

A TI-83 that doesn't say "Plus" or "Silver" is not okay. A TI-84 Silver with color is okay for my section, but some other math courses at TC3 don't allow it.

If you keep your eyes open for sales, or look at online sellers, you can probably to save a chunk of money on the calculator.

Buying used is also an option. These calculators are well built, so if you can get hold of a working used one it will probably be okay. Try it out before you buy.

Greetings, statistics buffs!

The textbook will be a free on-line textbook; I'll give you details later.

This email tells you about the calculator you will need. Any of these is okay:

- TI-83 Plus
- TI-83 Silver
- TI-84 Plus
- TI-84 Silver

A TI-83 that doesn't say "Plus" or "Silver" is not okay. A TI-84 Silver with color is okay for my section, but some other math courses at TC3 don't allow it.

If you keep your eyes open for sales, or look at online sellers, you can probably to save a chunk of money on the calculator.

Buying used is also an option. These calculators are well built, so if you can get hold of a working used one it will probably be okay. Try it out before you buy.

Error reports, permission requests: BrownMath.com/about

Updates and new info: http://BrownMath.com/stat15a/