Friday, September 30, 2005

Chapter 14 concepts

You will fully understand the confidence intervals and hypothesis tests after you have mastered Ch 10-Ch 13, but you can follow the patterns and use the tools for inference about the models you generated in Ch 3.

First, the confidence interval for the slope of the regression line is just a band around the estimate you created in Ch 3. You extend your interval t* standard deviations in each direction with your value of b as the center. The value of t* comes from the t-table using the confidence level C and df = n-2. Usually, the value of the standard deviation will be provided for you in the computer or calculator output.

The second tool is the hypothesis test. Look at the Minitab output on page 763. The values of b and SEb are given. The concept is that you are dividing the difference between the observed slope (b) and the default slope (0) by the standard deviation associated with the slope (Std dev of ddays) and call it the t-value. This is just like (x-mu)/sigma calculations for calculating z, except we have to use the t-table again. Find the probability (p) that we would get a t-value more extreme than the one we got and interpret. Remember how we found out how unlikely a z score of -2.08 was in problem 2.50? The interpretation is like that.

If p is small(usually anything less than .05), reject the null hypothesis. Therefore, the line through the data has a slope not equal to zero. Yippeeeee.

Sunday, September 25, 2005

Chapter 2 Test Questions

If you still have questions about the Chapter 2 test, please post your questions here. Kindly summarize the problem because different classes had different questions.

If you know the answer to someone else's question, please jump in and answer it!

You guys make me proud. . . every day.

Friday, September 23, 2005

Chapter 3 test is still Thursday

We just won't include the chapter 14 parts. Post your questions here. Do more exercises so you'll have good questions to ask on Wednesday. Please be safe. YKYMFS

I will be at CiCi's on Sunday.

Mrs. L

Saturday, September 10, 2005

Homework Help Hotline- post Q & A here

Post your question or post help for a classmate here. Don't be shy!

Wednesday, September 07, 2005

Flip50

Your assignment was to do problem 2.19 AND to determine what portion of your data fell in the "middle" three columns, then the "middle" 5 columns. Re-run the program a few times and record your new results. Post them to this site as a comment. Do you see a trend?

Friday, September 02, 2005

Assigned reading

Did you understand all of the probability and statistics in your book? Please identify the book you read and the concepts you need to know more about.

Please sign your posting with your first name and the class period. No last names, please!

Moneyball readers: Check this site for another take on your topic.
http://www.nytimes.com/2005/08/28/weekinreview/28leon.html

SAT analysis

What trends or patterns did you observe in the SAT data provided in class?