Math 151 , Fall 2005, Day 41 Mon. Dec. 5 Hit reload

Day 41  Reading: D&V Ch. 23 (two independent samples) thru p. 462, then 465-9.  You will not need to compute a two-sample t procedure by hand, but you will need to know how to identify the situation, to use SPSS, and understand the results. This is the end of the course material.  Begin reviewing.
Hand in 

Two independent samples 
E.  Repeat the analysis on the SPSS handout for the Polyester in landfill data.
p. 471, #1, 3 CPMP
6 a,b only Pulse rates
7 Cereal (SPSS: Data is in labs at Math151 D&V\spss data files D&V\dv01_24_07.sav )
8 Egyptians (SPSS: Data is in labs at Math151 D&V\spss data files D&V\dv01_24_08.sav, BUT it's in the wrong form!  It's in 2 columns as if it were Paired but it's not paired data.  You can highlight the 30 items in one column, copy and paste to the bottom of the other.  Then make a grouping variable to distinguish the two groups.)
17 Job satisfaction (What should you do? (Don't do it...))
12 a,b Memory
11 Hurricanes. Do a back-to-back tally of the two sets. Don't do the test, just think about appropriateness.  The answer in the back was a little misled by the inappropriate boxplot into thinking there are outliers, tho there aren't really, there's just "granularity" (small whole numbers here). 

 Read,
  to 
discuss 		 Optional 

Final exam:  Wed. Dec. 14, 2-5 pm.   Contact me ASAP me if you have a problem with this time.
The Final will be closed book, but bring one sheet with your notes, anything you like!
   Length 1 1/2 to2 times the length of the midterm exams; comprehensive but with special attention to the material covered since Exam 3, and at least a couple problems very similar to Exam 3.  Reading but not creating SPSS.

I'll be here Friday, middle of the day,  one day of Exam week before the exam, (Tuesday?) and by 11 on Wed. exam day.   Email me times that are bad for you.  I'd like to leave you free to do
  Friday, December 9
     Relaxation Workshop***          1:30 pm - 2:45
           Sommer Center
    Relaxation Workshop***          3:30 pm - 4:45
             Sommer Center
     ***These workshops will be led by Carlos dos Santos (www.carlosdossantos.com) and will focus upon using breathing, yoga, dance and body movement to reduce stress and anxiety.
 

What is the significance to Statistics of the Guinness Stout Bottle ?
Homework questions? Day 40

Look at transparency, 80% CI's for shoebox, n = 4.

Start here Monday
Chapter 24, Comparing two means"Two-sample tests". Chapter 24  Day 40

                /--- Group 1, n1---- Treatment 1---\
              /                                    \
 Random asst.                                       Compare results --"means"
              \                                    /
               \--- Group 2, n2---- Treatment 2---/
           (comparing 2 proportions is Ch. 22, which we skipped.  Goes similarly.)

To examine  the difference of the  two means, µ1 - µ2:
We use the difference of the two y-bars,  diff =  ybar1 - ybar2 = .

This almost fits the  t-model. Degrees of freedom are weird.(p. 454)

(For doing by hand, if you must: df = smaller of (n1- 1) and (n2- 1).) Will give a "conservative" result
From a computer:  df = complicated formula on p. 494 bottom.  Produces non-integer degrees of freedom.
Optional Example by hand
    CI for µ1 - µ2, difference of means,  is 
Test:  H0: µ1 - µ2 = 0 same as µ1 = µ2 , "no difference" "always"
        Ha: µ1 - µ2 > 0 same as µ1 > µ2Be careful with these, that you know which direction you want.
    or Ha: µ1 - µ2 < 0 same as µ1 < µ2 Often we label our variables "1" and "2" so that we expect µ1 > µ2
    or Ha: µ1 - µ2 0 same as µ1  µ2  (not equal)
        Calculate  find P-value

SPSS will do our computations when we are given raw data.  See handout. Datasets
Analyze>Compare means> Independent-samples t. We use the Equal-variances-not-assumed line of the results.

More time?  More about alphas, and testing as decision making (will not be on exam).

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