Math 151 , Fall '08, Day 4, Fri., Sept. 5 .after class, Hit reload to get most current version

HW assignment  Day4  (From Moore unless otherwise noted.)
(Re)Read Ch.2 thru p. 47. Do "check" p. 56,  2.15,17,18 (5#summary/boxplot). Read 53-55, "Organizing...". then: Finish Ch. 2. ("check" 2.19 (don't calculate. It's not #a), 20, 21, 22)
Do the 5-number summaries required here by hand (with a calculator if needed for means, finding middle between 2 numbers). 

Hand in Wed.:  (note,The first set of  problems is copied from Day 3 (postponed).  Label everything  Day 4.
5# summary, boxplots
p. 58, 2.29 fruit eating
p. 58, 2.30 newborns.  (I said I wouldn't make you make a histogram, but the data's already pre-binned, so do it here.) Also Describe the distribution--symmetric, skewed?
p. 58, 2.28 U. endowments.  They mean, what do you have to count in to, in the list, to locate the mean and quartiles?

p. 59, 2.34 guinea pigs survival:  For a) use the One Variable Statistical Calculator Applet at  http://bcs.whfreeman.com/bps4e   or on your text's CD (If you have an older, used book, it may be  in the datasets as if for BPS3e; ex02-23.dat).  Just observe the skewness.  For b), find the 5-number summary (easy since they're in order in the book), check your answers with the Applet results.  Draw the boxplot and compare with the histogram on your screen.  (with or without outliers, I don't care.)
p. 45, 2.5 Wood again. Go ahead and use the stemplot figures to find the quartiles.  Also make a boxplot.
p.58, 2.27 Flower length: Find the 5-number summary for bihai, from the stemplot p. 55. If you want more practice, do the other 2 by hand also, but you may just use the numbers from the answers in the back of the book.  Use them to make 3 side by side boxplots, and finish the problem as written.

+ + + +A few more + + + +
A.  You are driving on the thruway from Syracuse to Rochester and keep track of how many vehicles you pass and how many pass you.  You find that these 2 numbers are the same.  Your speed on the thruway is: (a) the Mean speed of the cars, (b) the Median speed of the cars, (c) the Modal speed of the cars.  Choose one, and justify your choice.

p. 60, 2.35  days of births, Canada The book's question is very open-ended.  Answer instead the questions just below this box*

p.55, 2.12 Rainforest logging.  Use the 4-step process, see below, p. 53-5&/or inside front cover.  Note that "state",  the first step, is usually "done"=the textbook statement of the problem.  The data are probably suitable for mean& standard deviation, but we don't have the SPSS power to do them easily yet, so use your hand methods--stemplots, quartiles, boxplots...  This is one where working together with others can have real benefits, since it's pretty open-ended.

"Read," to discuss (be able to answer in class)



 Optional 


* Questions for 2.35, p. 60 (Days of births, Canada):
A.  a) Which day had the lowest Median (and about what was that number)?
     b) Which day had the highest Median (and about what was that number)?
      c) Which day had the highest variability (spread), measured by:
                     --IQR (about what are the quartiles for this day)?
                     --Range (about what are min and max for this day)?
       d) Tuesday appears to be somewhat skewed.  Left, or Right skewed?
B. To compare the Canadian with the American data (p. 10, 1.4):
    a) Is the general pattern the same in the Canadian and American data?  Discuss briefly the common findings.
    b) (Following the 4-step method, p. 53:)
State the issue: Is the weekend/weekday difference greater in Canada or in the US (or are they similar?) 
Formulate an appropriate answer: In both countries, Tuesday is highest, Sunday is lowest. Relate the number of Tuesday's births to the number of Sunday's births for each country.  Proportion/ percents will show the relationship best, since different types of summary numbers are given for the two countries. ["Formulate" is where we make the to-do list. Solve is where we actually do it.] 
Solve:  For Canada,you have (part A) estimated the median number of births for Tuesday and also for Sunday, from the graph.  Take the number for Sunday, divide by Tuesday's number, restate as a percent. For U.S., use the numbers on p. 10, dividing Sunday by Tuesday.
Conclude, something like this:  " In Canada, on Sunday(s), the number of Sunday births was ___% of the number of births on Tuesday. In US [make the parallel statement.]  Therefore the difference is greater(?) in (Canada?US?).  This may indicate that proportionately more "planned births" occur in (Canada?US?)." (Remember we decided the most likely reason for the weekday/weekend difference was planned births--induced and Caesarians.)
    c)  The picture for 2.35 makes the difference between weekdays and weekend days look more extreme than it actually is.  Why/how?
    d)  To make the numbers more comparable,  (U.S. total of all births in a year of Sundays/Tuesdays, Canada median number per Sunday/Tuesday) it would be better if we had the Canadian Means.  (because mean times n = total).  Look at the boxplots and tell whether the Canadian mean for Tuesday would be less than the median, about the same, or more than the median.  Do the same for Sunday.

Sign in on the clipboard. .  Find someone you don't know and introduce yourself.  Introduce yourself to at least one person you know, in case they've forgotten who you are.Note Class members is up.  Check that you're correct.
Compare HW with others, tell me unanswered questions, write #s on the board.
Handing back Pretests (& collecting a couple)
Turning in HW out of class:  NOT Campus Mail!  Into 151 box outside my door, into yellow folder if it's there.

Notes, Day 3
Review median. HW questions? Day 3
Quartiles, 5#summary and InterQuartileRange, Boxplots.

Standard deviation: Computing it next time.  A single number to measure spread; "goes with" mean. Only good for roughly symmetric, unimodal distributions.

Organizing a statistical problem: Four-step process (pp. 53-5, & inside front cover) 
State: the issue to be explored, question to be addressed (real-world)  (In HW problems, often already stated.)
Formulate:  What statistical tools, measures, analyses should we use to answer the question?
Solve:  Carry out the process.  (May need to back up & try again.  You decide on mean, s.d., but stemplot shows badly skewed?  go back and decide on 5#summary instead.)
Conclude:  Give the conclusion as it addresses the real-world question/issue.
Any time left?? there wasn't: Begin p. 55, 2.12 in class in pairs (or 3's).  Decide what analyses to do; start doing them (make a copy for each person, if you won't be working together outside of class.)

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