- We have an exam in a week. Next time I'll give you a few more details on the types of problems you're likely to encounter. Today I'll give you a link to some problems relative to this stuff that appeared on my last exam over this material....
- Homework, Section 4.5 is returned (#4, 12 graded)
- #4:
- #12:
:
- While I do have a soccer ball at home, I just googled a soccer ball. Saying "I don't have a soccer ball." -- which many of you did -- is no excuse whatsoever.
- how many pentagons and hexagons?
- #4:
- Homework for Section 7.6 is due today.
- Assignment from section 7.5: pp. 581-: #1, 3, 4, 8, 12.
These will be attached to your upcoming exam, coming up 4/8, and constitute 10% of the exam. There will likely be an additional problem on the exam like these, to show me if you really understand the procedure. - We recently had an important election.
- Did you notice that the polls were all over the place? That some groups went to a "Poll of Polls"?
- Why do polls tend to differ?
- What's this Bradley Effect? Or the Reverse Bradley Effect?
- What is the Electoral College, and why can one candidate win more peoples' votes but lose the election?
- Sampling
- Samples versus Populations
- What is statistical bias?
- Cicada population data -- are we biased?
- Avoiding bias (e.g. the Literary Digest and the Landon/FDR election of 1936). Mindscape #5, p. 581.
- When is enough enough? Data, that is. (Too little is bad -- e.g. Bad, Bad, Biltong)
- Gold standard: random sampling
- Data we collect in a sample should be
- accurate
- unbiased (reflect the population truly - random sampling helps)
- "sufficient in number to reflect the population's variability"
- But: How do we get honest answers to life's tough questions?
- Are you rich?
- Do you cheat on your significant other?
- Do you have AIDS?
- Sampling with randomness -- sound like a good idea? Let's
try....
- Activity: Let's answer an embarrassing question:
are you male?
- We'll attempt to calculate the true rates of maleness and femaleness in class...
- Each person will flip a coin:
- If it's heads, answer "Male"
- If it's tails, answer truthfully.
- How do we now estimate the true rate?
- Guess that we'll have half the people say "Male" because they tossed a heads. The excess (above half) are truthful "male" answers.
- We guessed:
- M=7+8 (7 "true males", 8 "false males"))
- F=4 (4 "true females")
- True rate: 7/19
- Estimated rate: (15-9.5)/9.5=5.5/9.5=11/19
- Where did the 9.5 come from?
- More examples:
- Mindscape #2, p. 581.
- How likely are you to use your cell phone while driving?
- Now: what embarrassing question should we now attempt to answer? Who's got something they really want to know?
- How could we adapt this process to lose less of our data
(generalize, when you get a good idea!)
- with a die
- with two tosses of a coin?
- For next time: read section 6.2: The Dynamics of Change
- Today we start our unit on dynamics. The word "dynamics" has two slightly
different senses in what we will discuss:
- changes in time, and
- how one thing leads to another.
We start with examples of what I call "social dynamics". I suppose that dynamics come in three flavors:
- Good dynamics
- Neutral dynamics
- Bad dynamics
- Let's look at some examples, and discuss them. As we do so, think of examples of each kind, relationships between them, and other examples.