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.
| Hand in (all from Moore text unless otherwise noted). p. 20, 1.14 (hurricane hist) 1.17 (cf. age dist.) p. 17 1.9 (stem: SSHA) p. 22ff, 1.18 &19 (back to back HR) 1.24 (pop of states) |
Read, to discuss 1.15 batting, 1.16 coins |
Optional 1.26 teachers' salaries |
Pretests: order of operations, 3.5-6.2, 2(0) = 0 not 2,
#5
Data: Numbers
(usually)
in context: What, Who (how
many),
Why? When and Where? How?
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) Ordinal/nominal not in text!
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.
(Frequency
table)
Graphical summaries of data: Area
represents proportion.
Categorical:
Bar or pie graph (Bar chart ordered by size = "Pareto
chart"--not in text)
Pie only ok if showing all categories.
Quantitative: Histogram,
Stemplot (Stem-and-leaf), 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?
Stemplots
(Stem-and-Leaf)
are a powerful hand tool. Handout
Unordered first, then ordered if necessary. By tens, then
split?
Back
to back, comparing two groups.
Choosing a display (by hand): Note bottom of p. 38,
fig.
1.12, use of a to display a data set
of
size n = 7.
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, skewed (think smeared, or sliding) right or left),
(Humps: uni- or bi- modal (multi-) Two humps = two
"causes"?)
center,
spread--outliers?
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.
| Sievers home | Math151-/Fall04/Dayf2.htm | 10:30pm | 8/29/04 |