# Class 24: Pause for Breath

Back to Class Cancelled. On to Topic 19: Confidence Intervals: Means.

This outline is also available in PDF.

Held: Monday, 31 March 2008

Summary: We review issues we have studied recently, along with ideas and questions revealed in Topic 18.

Notes:

• I hope you all had a good break. Sorry for giving you work during break.
• I will continue to reserve time at the start of class to discuss issues on campus. (Today, I must also apologize for how the College deals with news.)
• I'm in the midst of rearranging the schedule. The other two sections have decided to visit chapters in a different order, and I'm trying to balance some of their changes. We will likely have the exam next Wednesday (April 9), rather than next Friday, and the first project will be due the following Monday (April 14) rather than this coming Monday (April 7).
• Activity 19-5 needs a record of the number of hours you slept last night. I'll pass around a sheet, and then quickly record the data.
• You'll find that today's activities require a lot of computer work.
• Due Wedneday: . Also do the preparatory work for Topic 20.
• Due: Topic 18 (in-class activities).

Overview:

• Review of confidence intervals and tests of significance.
• Discussion of Topic 18.

## A Short Review

A few of you had difficulty on topic 18 because you'd forgotten some key points from topics 16 and 17 (and, perhaps, earlier). You can refer to the book, if you find it necessary.

Confidence intervals?

• What is the critical value, z*?
• What formula do we use for the CI?
• How do we determine the critical value?

Hypotheses

• How do we express hypotheses about proportions?
• How do we compute the test statistic, z?
• What is the p-value?
• How do we compute the p-value?

Now, we're ready to discuss any questions you might have.

## Some Notes on Topic 18

Let's consider the main conclusions from topic 18. (And yes, I'll ask you to explain them.)

• Overall purpose of the topic?
• What are Type I and Type II errors?
• Activity 18-1: Generation M (Confidence Intervals vs. Tests of Significance)
• Activity 18-2: Pet Ownership (Statistical Significance vs. Practical Significance)
• Activity 18-3: Racquet Spinning (Statistical Significance)
• Activity 18-4: Female Senators (Sampling and Confidence Intervals)
• Activity 18-5: Hypothetical Baseball Improvements (Power)
• Activity 18-6: West Wing Debate

Back to Class Cancelled. On to Topic 19: Confidence Intervals: Means.

Disclaimer: I usually create these pages on the fly, which means that I rarely proofread them and they may contain bad grammar and incorrect details. It also means that I tend to update them regularly (see the history for more details). Feel free to contact me with any suggestions for changes.

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Samuel A. Rebelsky, rebelsky@grinnell.edu

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