Math 151 , Day 13, Mon., Feb. 25, 2008 Hit Reload...after class.

Hand In Wed "Day 12" Normal HW repaired + "Day 12": "Backward x problems"--Listed at bottom of Day 12 HW. Postpone Chapter 4 intro: : p. 92, 4.1 explanatory/response or just association     4.2 expl/ resp in an experiment (coral)     4.3 beer and blood alcohol, other variables p. 108, 4.24 date heights Make the scatterplot by hand.  Answer these questions instead of the ones given:  Describe the relationship--form, direction, strength,  (with only 6 points there's not enough data  to talk about outliers).  Is there any female dating a male shorter than she is?(Keep a copy of the graph, to use in the next hw.) p. 107 4.23 reading ability - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -   Scatterplots using SPSS.  (handout next time)  Graphs>Legacy Dialogs>Scatter/Dot > Simple Scatterplot.  Move variables from the lefthand  list to the X-axis (horizontal)  and Y-axis (vertical) boxes.  Don't forget to check Measure, and to add Labels. pp. 93& 96, 4.4 and 4.5 (SPSS) bird colonies(Save your file; you'll use it again for 4.10) p.96, 4.6 (SPSS) gas mileage ---From now on, make all scatterplots on SPSS!

Read, to discuss

Optional  Do now if you need the practice: Straight line graphing practice: A.  y = -10 + 3x, graph for 2<x<10. B.  y = 500 - 20x, graph for 0<x<10.

Exams returned.    Solutions

Comments:  2c) Mean = average, average = typical, therefore mean = typical.  NOT!
2b, 3c, skewness:  You have to look at the graph with the numbers increasing from left to right.
4d)  The mean is the sum total of all the individual numbers, divided by the sample size.  So to get the total back, just multiply the mean by the sanple size;  583,993.95 x 58 counties = 33,871,647.94 ~ 33,871,648 is pop. of CA.

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HW Questions?  Using z tables to go between raw values and proportions (percentiles)  See Day 12
   Optional Handout:  Normal probability practice  (end of class last time)
 
Handout:  Solutions p. 87, 3.46 surprising difference in tails
    p. 80-81 3.11 and 3.12 (locomotive adhesion, 2 dist's)   

"San Diego Reader"  --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).Discussion

More on backward problems!  Going from area to x: Day 11
= = = = = = = = = = = = = = = = = = = =
Start here Wed.
Relationships: (BPS4e Ch.4, at first to p. 98)  
Two Related quantitative variables  (We used side by side stemplots, boxplots, histograms to relate a quantitative variable to a categorical variable)
    "Just Related" or "explanatory & response?"
(Scatterplots)
explanatory = independent = "x" = horizontal axis ( = "cause", sometimes but not always)= predictOR
  response =    dependent = "y" = vertical axis      = ("effect ") =predicteED

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

Discussing Scatterplot
General Pattern                                      Deviations
Clusters?                                                      Outliers? (label if possible)
Form (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.

SPSS:   Graphs>Legacy Dialogs>Scatter/Dot > Simple Scatterplot.  Move variables from the lefthand  list to the X-axis (horizontal)  and Y-axis (vertical) boxes.  Don't forget to check Measure, and to add Labels.
  Some scatterplot data: govsal_vs_pay.sav  educ-v-mortality.sav  ,   studatsp03.sav
Handout on SPSS Scatterplots next time (BPS Ch. 4&5)