1. Homework: pg. 333 #1, 2, 4, 7, 8
1.) Population: All local businesses. Sample: the 73 businesses that return the questionnaire, or the 150 businesses selected. Nonresponse rate= 51.3% 2.) A. An individual is a person; the population is all adult US residents for that week. B. An individual is a household; the population is all US households in the year 2000 C. An individual is a voltage regulator; the population is all the regulators in the last shipment

2. 4.) We can never know how much the change in attitudes was due to the explanatory variable (reading propaganda) and how much to the historical events of that time. 7.) Only persons with a strong opinion on the subject will respond to this advertisement. 8.) Letters to legislators are an example of a voluntary response sample- the proportion of letters opposed to the insurance should not be assumed to be a fair representation of the attitudes of the constituents.

3. Practice pg. 341 #10
Choose 3 resorts, using Table B, starting on line 131

4. Practice pg. 342 #13
A poll of opinion in CA uses random digit dialing to choose telephone numbers at random. Numbers are selected separately within each CA area code. The size of the sample in each area code is proportional to the population living there.
A.) What is the name for this kind of sampling method?

5. B.) Here are the area codes in CA: A different method would be to choose 10 area codes using a SRS using Table B starting at line 111.

6. 5.1 Cautions about Sampling

7. Cautions about sampling
Bias—when you favor one outcome
Poor designs lead to bias

8. Types of Bias
Undercoverage bias—some groups of the population are left out of the process of choosing the sample
Nonresponse bias—an individual chosen cannot be contacted or does not cooperate
Response bias—behavior of the respondent or interviewer changes the answer
Females asking about feminism
Asking about illegal behavior
Wording of questions

9. Inference about the Population
Inference—drawing conclusions
One sample is different than another
There is always a margin of error
Larger samples are more accurate than smaller samples

10. HW: pg 349 #21, 24, 27-31