Math 151, Fall 2005, August 29, Day 2 Hit reload to get most current versionmodified hw

Day 2 (Mon. Aug. 29): Reading:  Reread D&V thru p. 18. (We'll come right back to pp. 18-24) Read Ch.4 thru p. 46  (Re-expressing p. 44 optional), + stemplot  handout. Activstats 3-1, 4 all.  Ahead, D&V Ch.3 pp. 18-24. Activstats 3-2.
We'll start using SPSS probably Friday--have class in the computer lab.
Italicized notes give me a hint which problem it is. (my comments0
    Problems on the same line usually cover similar issues.
Needed for HW: Stemplot, rounding when there are more than 2 decimal places?  Handout says truncate (round down), D&Wtext says round to nearest.  Tukey, the inventor, said truncate; throw away the trailing digits; I agree.  This is supposed to be fast--rounding to nearest slows it down.  I encourage truncating but you can do it either way and be right.  If you truncate, your stemplot may look a little different from the text answers. (A stemplot is hard for a computer to do, but some packages do. For them, rounding to nearest is easiest.  SPSS truncates, which is hard for a computer.)
Hand in (all from D&V text) 
Ch 2 p.13,  4 Oscars, 5 Bears
Ch 3 p.28, 5 Death;
 12 Teen Tech II 
 13 Auditing [I could disagree w/answer to b]
A) On a separate sheet:  First for the20 cases with the  right hand, then for 20 with the left hand: Make a frequency table for the variable "color"  in your Circle experiment, with a column of Counts (how many "red", how many "blue"....), and one of Percents (relative freq.).

Ch4 p 50 Work on Ch4 problems, but they will all be part of Day 3 HW (Due Friday) 
Creating:
 12 bird species (10's as leaves, split 5 leaves per stem is good.  Big outliers)
 18 Marijuana (stem &leaf)
Describing: 
 5 Heart attack stays
 9 Wineries: Make a) "under 60 acres". Book's answer to b is screwy, why?
 14 Pop. growth

 Read, be able to discuss in class
Ch2 9 Babies, 10 Flowers
Ch3  11 TeenTech I
 
 
 

Ch4

Work on Ch4 problems, but they will all be part of Day 3 HW (Due Friday)
Creating: 
 17 Acid rain Look at answer, note stems used 
Describing:
 7 Cereal sugar
 6 Emails (I think the answer book does a crummy job)
 19  Hosp. stays Do a only.  Read answer to c.  Most mothers & babies go home in 2 days now.  What W's are crucially omitted here? 
 

 Optional 

 
Introduce yourself to your neighbors--sides, front & back.  Group  in 4's or 5's. Check for Homework questions?
Each group make common list of things you might like to know about your mousing skills ("Circle experiment")
    Put your names on the common list, hand in.
  Keep your data from the circle experiment; hand in just the answers to B)
Hand in Info sheets, Math pretests if you didn't.   Sign in.
  Helpers    Fay's hours are now posted. 10:30-11:30 MWF, 11-12 T Th.  Go in and meet her.
Honor code:  This community of learners is a rare and fragile thing.  Trust is the foundation of its structure.  Betraying the trust damages the whole community.  Please do not betray my or your fellows' trust, and I will do my best to reciprocate.  The flip side of this is that if you do betray our trust, I will definitely pursue it in Community Court.  See my door for an interesting psychology experiment on this issue.

Handouts: Bar&Pie, Stemplot
Missed class? handouts  are outside my door (Mac 102), 151 box, white folder
Data:  Numbers  in context:  Who (are the cases & how many =n),What (&units),  When and Where,  How, Why?
   Context for height, hair color, shoe size, pulse rate:  Any problems with the way I did it?

Variable (possible values), individuals (cases)
        Categorical (ordinal--has natural order or &&nominal--just names)
    or Quantitative (can add, average--measured on a ruler-type scale) Units?! ("calories"?)

OBJECTIVE (from syllabus): To learn many of the ways in which data can inform us about the world, focusing on

   "Circle experiment"
    -- how to present your individual data--so it answers your questions.
    -- design of the experiment: what things were done to eliminate "lurking" or "confounding" variables--that might mess up the data.
    -- inference:  Data represents what you DID.  Would you get similar results if you did it again?  Can we infer from our class results to other people?  The techiques and rules  for dong so.

Distribution of one variable:  what values, how many (or what proportion) of each.
        "Make Piles" -- Frequency table:  count,  percent="relative frequency"  (Hair color)

Graphical summaries of data:  Area represents proportion. ="Area principle"
     Categorical: Bar or pie graph  (Bar chart ordered by size =&& "Pareto chart"--not in text)
             Pie &&only ok if showing all categories (part of whole) + no overlap of categories.
              .  Pie by hand?  Template handout

    Quantitative: Histogram, Stem-and-leaf (Stemplot), Dotplot
      (I will only require you to read, not make histograms by hand. You'll Make stemplots and dotplots by hand)
       Pretest:  Restate #5 as histogram of 100 "5-volt" batteries tested for actual voltage.
              The proportion with voltage < 1 is 20%.  The proportion with voltage < 3 is 60%.
               a) What proportion have voltage beween 1 and 3?  b) What proportion have voltage > 3?

   Stem-and-Leafs are a powerful hand tool.  Handout
            Unordered first, then ordered if necessary.  By tens, then split?
        Back to back, comparing two groups. (p.51, #14)

Choosing a display (by hand):
    A dot plot is most useful for n = 3 to about 15-20, or when the data only fall on a few values (just stack the dots up).
    A stemplot is good for continuous data, smeared around; you can do 100 values in 3-5 minutes.

Describing:  Pattern-- and deviations from it
   Shape (symmetric, or skewed (think smeared, or sliding) right or left),
        (Humps: uni- or bi- modal (multi-)   Two humps = two "causes"?)
        Some special shapes:  uniform (p. 40)  && J-shaped (#6 p.50) bell-shaped (Ch 6)
   Center, Spread
   Outliers,  gaps ? (different groups, sources?)
What do we see?  What can we infer? (Introduction)
    Data source? Lurking variables?
    Variability happens.  Things settle down on average, BUT conclusions are never certain.
    Statistics gives us a language for talking about uncertainty.


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