1. Alg 2/Trig Honors – Stats Unit Day 8
Statistical Studies
Alg 2/Trig Honors – Stats Unit Day 8

2. Surveys
Surveys are relatively easy to conduct, provide quick results, and can often provide interesting/captivating media headlines.
Keys to using a survey for collecting data:
Quality of Questions
Selecting Participants

3. Quality of Survey Questions
Quality of Survey Questions – Loaded questions, leading questions, confusing questions Sample Survey Question: “Do you like the cafeteria’s food?” Versus “For each of the following items offered by our cafeteria, identify whether you:” a. Like the Item b. Do NOT like the Item c. Have never tried the Item

4. Quality of Survey Questions
“Don’t you think that a small increase in property taxes is a worthwhile investment for improving the quality of education for our children?” Versus “Our town is considering a 4% increase in property taxes to raise funds for a new school to be built. What is your opinion on the proposed increase in property taxes? Strongly in favor In favor Neutral Oppose Strongly oppose

5. Selecting Participants
 How are participants selected? Random, Convenience, Volunteers, Compensated
1936 Election - Alf Landon versus Franklin D. Roosevelt – Literary Digest Poll versus George Gallup
Ideally, survey results are used to generalize about the larger population. To do requires sampling a large enough portion of the population and doing so in an appropriate way

6. Observational Studies
Observational Studies do not attempt to impose a treatment or influence the responses of those being studied (A survey is really one type of observational study)
 Sample Observational Study
Researches investigate the link between hours of sleep the night before an exam and performance on the exam

7. Observational Studies - Correlation
The main disadvantage of an observational study is that a cause-and-effect conclusion cannot be drawn from any observed relationship.
Correlation does not imply causation!
Correlation Examples:
There is a positive correlation between ice cream sales and drowning accidents
There is a positive correlation between the number of books in a home and the earnings potential of a child
There is a positive correlation between the number of people killed by venomous spiders in a year and the number of letters in the winning word of the National Spelling Bee
Spurious Correlations -

8. Experiments
An experiment imposes a treatment to see how it impacts the response. If an experiment is well-designed and conducted, experiments enable a cause and effect conclusion to be made.   
Designing a good experiment:
Include a large enough sample size
Choose subjects that accurately represent the target population
Assign subjects randomly to the treatment and control groups
Controls for possible confounding/lurking variables
Is ethical