Understanding Statistics					 J.R. Rasmussen

					Class 9 Outline

I) Today's Class

	A) Hand back Quiz 1

	B) Keep assignment 4, Extended assignment 4 due 11/04/09
	
	C) Recap of last class
		1) understanding the New York Times poll
		2) The normal probability distribution

	D) Introduction to sampling distributions


II) Quiz 1:  discussion of the questions


III) Recap of last class:  New York Times Poll:  computer simulation

	A) General setup
		1) How we view poll results as a binomial distribution
			a) Pr(success)=.4, n=the size of our poll was 100

		2) we looked at a poll 100 people
			a) Binomial set up:  Pr(success)=.40
			b) look at 40 ± 10
			c) group exercise: looked at the experimental results as if each student did 125 polls of 100 					residents and then we did 10000 polls of 100 					residents.
			d) then we looked at the pictures
			e) then we calculated the relative frequencies of being between .37 and .43
			f) students reported their values: all about 95 % 
	
IV) Recap of the normal distribution

	A) Why we need to learn about

	B) probabilities were the area under a curve

	C) The bell shaped curve:  graph
		1) the normal(0,1) curve and its table or probabilities
		2) How we use the table: examples of different regions

IV) Recap of the normal distribution  continued

		3) Other normal curves X and how we calculate
			a) converting to the standard normal curve 
			 b) how we convert, the z* values: (x-"mu")/"sigma"
			c) we did various examples
		4) normal curves on Excel:  the Excel syntax =normsdist

V) BREAK	


VI) Putting it all together

	A) General picture: real world vs. random variable world

	B) Sampling Distributions
		1) random variable X
		2) random sample from X of size n
		3) formalizing what we did on Excel
		4) We look at the mean of the sample: a new random variable
		5) Rule 1 and 2 for the mean and standard deviation of the new variable which is the mean of the sample
		6) Apply Rule 1 to what we did
		7) Apply Rule 2 to what we did

	C) The New York Times poll:  one more time

		1) Group exercise: generating a "picture" of the poll
			a) the New York times poll was sample of n=979 now set Pr(S)=.60  
			b) use the random number generator on Excel togenerate 10000 polls  (place them in a1:a10000)	
			c) calculate the proportion of the poll in b1:b10000
			d) counting the frequencies 
				i) set up bins: .55, .555, .56, .565, ... .65 in d1:d21
				ii) calculate the frequency:  first highlight cells e1:e22, then =frequency(b1:b10000,d1:d21)
			e) Use bar wizard to obtain histogram 

		2) Rule 1 and Rule 2 for our new 10000 polls  
			a) Rule 1: students calculate the average of their 10000 polls
			b) students report their averages
			c) Rule 2: students calculate the standard deviation 	of their 10000 polls
			d) students report their standard deviations
					
	VII) Hand out assignment 4 extended , due Wednesday 11/04/09