Handouts: Stemplot, Pie & Bar Template
Missed class? handouts are outside
my door (Mac 102), 151 box, white folder
Day 2(Wed. Feb. 2): 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 Monday--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&W
text 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 the right hand, then for the left hand: Make a frequency table for the 20 colors in your Circle experiment, with a column of Counts, and one of Percents (relative freq.). Ch4 p 50 Work on Ch4 problems, but they will
all be part of Day 3 HW (Due Monday)
|
Read, be able to discuss in class
Ch2 9 Babies, 10 Flowers Ch3 11 TeenTech I Ch4
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Optional
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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"?)
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
Will start here Wednesday:
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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