1. Bias and Sampling Mr. Zummo August 27 th, 2012

2. Bias After reviewing the materials about the dress code, what do you notice about the different responses from the different people?

3. Bias (Defined) A study, a question, a research design, etc. is declared to be BIASED if it systematically favors certain outcomes. You really want something to happen Why do people have biases?

4. “Don’t you think that Chocolate is better than Vanilla?” A.) It’s just fine. B.) Do you prefer Chocolate or Vanilla? C.) Given that most people like Chocolate, do you think that Chocolate or Vanilla is better?

5. “Do you prefer the cold, rainy days of Winter, or the warm and pleasant days of Spring?” A.) It’s just fine. B.) Would you prefer to stay at home in the Winter or to enjoy being outside in Spring? C.) Do you prefer Winter or Spring?

6. Do you think that Fenger students should take AP Statistics? A.) It’s just fine. B.) Do you think that Fenger students should take AP Statistics, a course that requires a lot of time? C.) Would you take AP Statistics even if your friends were not enrolled in the course?

7. Change the Question Do you agree that a national system of health insurance should be favored because it would provide health insurance for everyone and would reduce administrative costs? A.) Would create response bias B.) Would not create response bias

8. Change the Question? How many movies have you watched in a movie theater within the last 12 months? A.) Would create response bias B.) Would not create response bias

9. Question Is there anything in your life where you favor a certain outcome, or really want something to happen? –When you text somebody, what do you expect to happen? –What about yourself? Defending Friends –TV advertising –Music

10. Assessment In partners, figure out a way to reduce or eliminate bias in your everyday life.

11. Class Task The goal: Develop a survey to gain as much information about the class as possible. Topics to consider –What type of questions should we ask? –What is the purpose of the survey? –How many questions should be asked?

12. Sampling Population –The entire group of individuals that we want information about is called the population Sampling –Involves studying a part in order to gain information about the whole. Census –attempts to contact every single individual in the population.

13. Different Types of Sampling Voluntary Response Sample Convenience Sampling Simple Random Samples

14. Voluntary Response Sample Definition: Consists of people who choose themselves by responding to a general appeal. TV host ask population to call in to a yes or no question. The results are from the.

15. Convenience Sampling Definition: Choosing individuals who are easiest to reach Shopping mall example

16. Simple Random Samples A Simple Random Sample (SRS) of size n consists of n individuals from the population chosen in such a way that every set of n individuals has an equal chance to be the sample actually selected.

17. Questions to Consider Which of the three sampling techniques minimizes bias the most? Which type of sample did we take for the class survey?