Math 151 , Day 10, Friday, Feb. 23, 2004 After Class

HW Day 10:  Bring questions for exam.!!
Read Ch. 2 (Examining relationships), 2.1  pp. 78-91.  and  ahead 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

Relationships & Scatterplots: 2.1 Hand In: 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  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  Begin SPSS Scatterplot, Hand in all next Wednesday Scatterplot handout is outside my door (white folder) if you want to work ahead. ---From now on, make all scatterplots on SPSS! SPSS Scatterplot Handout:  Use the handout and govsal_vs_pay.sav  data file to use SPSS and answer questions 1-5 (page 3 of handout).  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, or Exclude them from the graph (handout p. 2).  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 printed plot, and connect the means dots.

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

HW Questions? 
 Need more normal distribution practice?  Get Handout if you didn't last time.
    Handing out:  Sample exam 1 questions+Ch 2 scatterplot extra page.  (Extras in white folder outside my office)
               Solutions on reserve, + outside my door.
--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).*
= = = = = = = = = = = = = = = = = = = =
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 ")

(Living histograms:  Height vs. weight, Height vs. gpa)

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)
  Some scatterplot data:  educ-v-mortality.sav  ,   studatsp03.sav
Handout on SPSS Scatterplots etc. (Moore Ch. 3)
govsal_vs_pay.sav  is the file used for most of the handout.