p. 227, 9.4, 9.5, 9.6 treatments, factors,
Can do now: Hand
Monday after Break, Day 24 Separate
|Read, to discuss
p.220, 8.38 3 over 21
p. 221, 8.43 guns
p. 214, 8.13, 8.14 biases.
p. 222, 8.44 wording survey questions p. 222, 8.46 Canada healthcare
p.210, 8.10 Sampling pentacostals (size)
= = = = = =
p. 219, 8.37
internet Use table B (more practice)
p. 220, 8.37 seat belt use (bias)
Exam 2 handed
Link to statistics,
comments, solutions. I may make a
few more comments on content on Wednesday
Midterm grades will be posted by Friday afternoon; will be slanted pessimistically at the high end.
Because it's so important to have control of the Normal distribution:
Makeup work to get 90% of the 42 Normal distribution points. To me by 3:30 pm Day 27 (Monday, April 2--2 school weeks). START NOW! (Print the sheet if you need it.)
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
On the sign-in clipboard. Next to your name: Put the number of East Asian surname individuals in your SRS, (p. 209 8.7) Be sure it's in your HW also, with the names of your sample! If you did it with another person, put that on the clipboard!
recap: Ch. 8&9: Producing Data: Aim:
create data sets that will allow us to make inferences to
larger world than just the data we have.
(SAMPLING) BIAS: The design of a study is biased
it systematically favors certain outcomes.
Non-probability samples (sampling badly): Voluntary response sample , Convenience sample
Our main sampling design:
Simple Random Sample (SRS) of size n: n individuals chosen in such a way that every possible set of n individuals has an equal chance of being chosen.
Homework Questions Day 20
Using Random Number Table. See Day 20 for details.
(Simple Random Sample Applet, done last time. Enter population size, sample size, hit Reset, then Sample.)
See Day 20 for rest of details on Ch. 8:
Some more sources of bias:
**Undercoverage: One possible source of undercoverage: your Sampling frame excludes some individuals.
**Wording of questions
A random sample (p.210) is from a design where impersonal chance is used to pick the individuals. SRS (p. 205) is the most straightforward. More sophisticated methods are often used, but they're optional this term. (More info)
+ + + + + + + +
Larger (RANDOM) samples give more accurate results than smaller random samples.
(but Not because you have more of the population.)
More discussion of terms used in sampling
= = = = = = = = = = = = = = = = = = = = = =
Chapter 9, intro
Observational Study: Observes individuals, measures variables, does not influence the responses. (ch.8)
Sometimes observe individuals who are (more or less) conveniently at hand, or, better,
Take Sample from a population, examine it.... (ch.8)
Experiment: Imposes treatment on individuals, to see how the treatment influences the response. (ch.9) Confounding: Two variables (explanatory or lurking) are confounded when you can't sort out their effects on a response variable. (Rats: Mothers' grooming causes sociability, or inherited sociability from mothers who like to groom? Health: Coffee and cigarettes (till recently)).
Different jargon; different traditions.
Do something to:
"Experimental Units" = "Subjects" = individuals.
Treatment: Specific experimental condition we impose on one or more subjects.
Factor: Explanatory Variable we manipulate.
There will be Specific values of a factor that we set. (Sometimes called "levels")
Response variable(s) Results that we measure.
E.g. Corn planting (HW day ??, p. 116, 4.32) 1 factor = planting rate. 5 different values (levels). 16 individuals (plots of ground). Response: yield per acre.
E.g. 2 headache medications, in combination?
A two-factor experiment, each with 3 values (levels). 9 possible treatments.
Factor A: Aspirin: values: None, 500 mg, 1000 mg
Factor B: Caffeine: values: None, 50 mg, 100 mg
Response variable: reported pain relief
|None||500 mg||1000 mg|
|None||Treatment 1||Treatment 2||Treatment 3|
|Caffeine||50 mg||Treatment 4||Treatment 5||Treatment 6|
|100 mg||Treatment 7||Treatment 8||Treatment 9