1. STAT E100 Section Week 4 - Sampling

2. Review  Knowing how to read SPSS Output  Email addresses  Sample vs. Population  Organizing the terms in your own thoughts

3. Review Ŷ = -0.277 X value of extravert + 4.808

4. Key Concepts:  Correlation ≠ Causation

5. Key Concepts:  Types of Association (causation vs. non-causal from confounding/lurking)  Design of Experiments and Survey Methods  Randomization (CRD vs. block randomized)  Random Sampling (SRS vs. stratified vs. cluster vs. multi-stage)

6. Key Concepts:  In stratified sampling, the population is divided into homogeneous groups called strata, using an attribute of the samples. Then members from each stratum are selected, and the number of samples taken from those strata is proportional to the presence of the strata within the population.  In cluster sampling, the population is grouped into clusters, predominantly based on location, and then a cluster is selected at random.  In cluster sampling, a cluster is selected at random, whereas in stratified sampling members are selected at random.  In stratified sampling, each group used (strata) include homogenous members while, in cluster sampling, a cluster is heterogeneous. http://www.differencebetween.com/difference-between-stratified-and-vs-cluster- sampling/#ixzz2fwcoHvwu

7. SAMPLE QUESTION #1 1) Causation vs. Association For each example, list whether we you believe there is causation, or some confounding/lurking variable (please list any possible lurking variables, and draw the relationship graph): a) Smokers have higher rates of lung cancer. b) Smokers tend to have lower rates of asthma. c) Couples that live together before being married are more likely to get divorced later. d) Dog owners live longer. Questions for thought: What is y? What is x?

8. SAMPLE QUESTION #2 2) Randomization In order to determine whether or not Tylenol reduces the severity of headaches, an investigator wants to create a clinical trial answer this question. She has 12 people signed up for the study, listed below. Using a random digit generator to assign the participants to either placebo or Tylenol: SubjectTreatmentSubjectTreatmentSubjectTreatment Alex Erica Isaac Billy Fred Jess Carol Gary Kelly Dave Helen Laura

10. SAMPLE QUESTION #2 2) Randomization In order to determine whether or not Tylenol reduces the severity of headaches, an investigator wants to create a clinical trial answer this question. She has 12 people signed up for the study, listed below. Using a random digit generator to assign the participants to either placebo or Tylenol: SubjectTreatmentSubjectTreatmentSubjectTreatment Alex 10Erica Isaac Billy 09Fred Jess Carol 73Gary Kelly Dave 25Helen Laura

11. 3) Sample Survey In 1987, Shere Hite authored a book entitled Women and Love: A Cultural Revolution in Progress (http://www.amazon.com/Women-Love-Cultural-Revolution-Progress/dp/0394530527) which reported some very captivating survey results on women's intimacy and love relationships. She reported the following: 84% of women are “not satisfied emotionally with their relationships” (p. 804) 70% of all women “married five or more years are having sex outside of their marriages (p. 856) 95% of women “report forms of emotional and psychological harassment from men with whom they are in love relationships” (p. 810) 84% of women report forms of condescension from the men in their love relationships (p. 809) Hite collected her sample by sending surveys to 100,000 women via snail-mail. She mailed the questionnaires to addresses collected from mailing lists of groups of women professionals, counseling centers, church societies and senior citizen groups. She received about 4,500 surveys in response. Obviously, this is not an example of great survey sampling. For Hite's data collection techniques, give an example of each of the following: Selection Bias Response BiasNon-Response Bias SAMPLE QUESTION #3

12. 3) Sample Survey In 1987, Shere Hite authored a book entitled Women and Love: A Cultural Revolution in Progress (http://www.amazon.com/Women-Love-Cultural-Revolution-Progress/dp/0394530527) which reported some very captivating survey results on women's intimacy and love relationships. She reported the following: 84% of women are “not satisfied emotionally with their relationships” (p. 804) 70% of all women “married five or more years are having sex outside of their marriages (p. 856) 95% of women “report forms of emotional and psychological harassment from men with whom they are in love relationships” (p. 810) 84% of women report forms of condescension from the men in their love relationships (p. 809) Hite collected her sample by sending surveys to 100,000 women via snail-mail. She mailed the questionnaires to addresses collected from mailing lists of groups of women professionals, counseling centers, church societies and senior citizen groups. She received about 4,500 surveys in response. Obviously, this is not an example of great survey sampling. For Hite's data collection techniques, give an example of each of the following: Selection Bias Response BiasNon-Response Bias SAMPLE QUESTION #3 Sample does not represent entire populationOnly those who feel the strongest willHow were the questions worded? What about women from universities?respond.