Understanding Statistics					 J.R. Rasmussen

					Class 12 Outline

I) Today's Class

	A) Confidence intervals revisited

	B) Student's t-curve

	C) Quiz 2: In class, open book & open notes on Wednesday 11/18/09

	D) Hand out assignment 6 due on Wednesday 11/18/09


II) Last Class 

	A) Any open items?

	B) Confidence intervals:  another application of rules 1-4.
		1) Intuitive idea: using a random sample we want to have a method to construct an interval
		 which will represent a range of plausible values for the unknown population mean “mu”. 
		 We also want to have some way to measure how confident we are of our method.
		2) Key to our method was Rule 3-4 and the Z-table
			a) we looked at standard normal case first to find an interval with 95% area under the normal curve
			b) then we replaced Z using Rule 4 
			c) summary of what we did:  the "general" formula  for”pi” and “mu”

III) Confidence intervals for “pi” : revisited 

	A) Group exercise
		1) use the Z table to find a 99% area
		2) now apply this 99% z-value to construct a 99% confidence interval 
		for the data on affirmative action from example 9.4 on page 380

	B) Group exercise: problem 9.13 (b), page 386
			problem 9.18 b, page 387 

	C) Group exercise:  How large a sample must we take to have a 95% confidence interval for “pi” with total length .03



IV) BREAK



V) Confidence intervals for “mu”

	A) Restate the general formula for confidence interval for “mu” using Rules 1-4
		1) formula on page 389
		2) do example 9.7 pages 389-390

	B) The problem with the formula:  how do we know “sigma”

	C) How we construct a confidence interval for “mu” when we don't know “sigma”
		1) estimate “sigma” by s from the data
		2) the t-curve
		3) how to use the t-curve instead of the Z curve
			a) the sample size and degrees of freedom
			b) formula for confidence interval with t-critical value:  page 393
		4) example 9.9 pages 396-397

	D) Group exercises:
		1) page 399, 9.31 part b
		2) page 401, 9.39 part a
		3) page 401, 9.41 part a


VI) Homework

	A) Remember assignment 5 is due Monday 11/16/09; you might want to make a copy of your assignment
	 before you turn it in on Monday so that you can make notes on the solutions
	 and use the copy during quiz 2 on Wednesday, 11/18/09

	B) Remember assignment 6 is due on Wednesday, 11/18/09

	C) Homework working session