Math 151 , Day 11, Monday, Sept 23, 2002  After Class

-Exam 1  Friday Sept. 27, in class, closed book.  Bring a simple calculator. I'll give you copies of the Normal table.
Covers through Monday's HW.  You will need to read SPSS output, but not tell how to produce any. You will need to calculate "by hand" a standard deviation for four numbers. (As well as medians, quartiles, etc.)   Problems like HW + some true-false or multiple choice types.
Amanda--regular hours + Thursday night from 6-8pm.
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Handout on SPSS Scatterplots etc. (Moore Ch. 3)
govsal_vs_pay.sav  is the file used for most of the handout.
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HW Day 11:  Bring questions for exam.!!
Read ahead Ch. 2 (Examining relationships), pp. 78-91.  and   2.2 (correlation) You do not have to be able to calculate r by hand.  You should be able to guess roughly at an r for a swarm of data; as p.101, fig. 2.9, and know and  be able to use facts 1 thru 7, p. 100
All Postponed: Relationships & Scatterplots: 2.1
p.81, 2.1 (rel. or explan/resp) 
Do 2.17a, p.98, graphing by hand! 
p. 91ff, 2.8 gpa vs. IQ 
  2.10 states'mean/median income 
-From now on, make all scatterplots on SPSS! 

p.87, 2.6 (SPSS) gas mileage
p.89, 2.7 (SPSS) metabolism Using the pre-made data set, graph the males and females simultaneously.   If you want to print just the females, change the male points' color to white.  Save your data file and output file for problem 2.22, later.
p. 95, 2.14 (SPSS) (teachers' pay vs.no HS)

(This problem looks forward to Sec. 2.3, sort of)  p. 95, 2.13 corn plant density. (SPSS) Import the data from the text file. Notice how the data is entered for SPSS--not as displayed here! but with the first column giving planting rates and the second giving yield.  Make a scatterplot.  You can find means for the separate groups as we did before (in Explore, rates to the Factor list).  Graph the means by hand on your plot, and connect.

 Read, to discuss 
 

 p. 82, 2.3 (Breast CA vbles)

 Optional (more practice) 
 

p. 92, 2.9 hotdogs&sodium
2.11 Wine vs. heart disease
(Activstats: Ch.7, Scatterplots, pp. 1&2 (p.3 is optional))
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HW Questions?   Need more normal distribution practice?  Get Handout. Review time?
--What proportion of pregnancies last 310 days or more?  z = (310-266)/16 = 44/16= 2.75.  Area above 2.75 = .0030.
        3 in a thousand pregnancies last that long.  Pretty rare.  Is "San Diego Reader" one of the 3-in-a-thousand, or is she lying?  (this is the kind of question we deal with in Significance Testing, part 3 of the course).*
Start here Wednesday
Relationships: (Ch 2 Intro and Sec. 2.1)
Related quantitative variables
    "Just Related" or "explanatory & response?"
(scatterplots)
explanatory = independent = "x" = horizontal axis ( = "cause", sometimes but not always)
  response =    dependent= "y" = vertical axis      = ("effect ")

Discussing Scatterplot
General Pattern                                      Deviations
Clusters?                                                      Outliers? (label if possible)
Shape (linear, curved, ...?)
    Strength of relationship (how unfuzzy)  "Weak, moderate, strong"
Direction
    Positively associated:  y increases as x increases (generally).
    Negatively associated:  y decreases as x increases.

Mark subgroups differently to do comparisons. (Subgroups defined by categorical variable, like Sex, Region of country)


Correlation (2.2)
Website,  http://www.whfreeman.com/scc,
ClickNetscape toolbars to minimize them, if needed.
  Choose "Statistical Applets",  Correlation/Regression.  Play with data points, observing the Correlation Coefficient.
    Check in the "Show Mean X &Mean Y lines" box.  See how much is in each quadrant.
Sievers home  Math151-Fall02/Day11.htm   1pm  9/23/01
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*Bear in mind that there were around 400,000 births in California in 1970. (I'm guesstimating.  There were 605,694 births in 1990, and the population of California in 1970 was 2/3 of that in 1990).  So a 3-in-a-thousand event would occur in 3x400 = 1200 births--there would be 1200 women in San Diego Reader's position (many of whom wouldn't know it.)  Rare events DO happen--it's not really fair to only notice and question them AFTER the fact.
Note--pregnancy in 1970 usually didn't involve the level of medical intervention (ultrasound, inducement of labor, etc.) it often gets now.