1. “Do Now” In your notebook,
Define “Bias” in your own words and how it will impact your survey you have created for your portfolio
Be ready to discuss your answer
Level 0

2. Is your desk cleared off?
Agenda
Write down HW
Study for Quiz #5 on Thursday
Portfolio is due on Friday
Do Now
Review Do Now
Quiz #4 Recap
“Bias and Parameters” Lecture
Exit Slip
CW = Work on portfolio
Is your desk cleared off?

3. Bias and Parameters
December 3, 2012

4. Vocabulary Words Bias Sampling Bias Undercoverage Nonresponse Bias
Open-end Question
Close-end Question
Nonsampling Error
Sampling Error

5. Types of Bias
Bias: the results of the sample are not representative of the population
1. Sampling Bias
2. Nonresponse Bias
3. Response Bias

6. Sampling Bias
Means that the technique used to obtain the individuals to be in the sample tends to favor one part of the population over another.
Any convenience sample has sampling bias because the individuals are not chosen through a random sample.
Example: A voluntary response sample will have sampling bias because the opinions of individuals who decide to be in the sample are probably not representative of the population as a whole.

7. Undercoverage
Occurs when the proportion of one segment of the population is lower in a sample than it is in the population.
This occurs in sample bias (REMEMBER ME)
Checkpoint: Define Frame
Undercoverage can result because the frame used to obtain the sample is incomplete or not representative of the population.

8. Nonresponse Bias
Exists when individuals selected to be in the sample who do not respond to the survey have different opinions from those who do.
Simple Terms: Occurs when individuals selected for the sample do not wish to respond or the interviewer was unable to contact them.
Examples?
What can you do to combat nonresponse bias?
This occurs in every type of survey.

9. Response Bias
Exists when the answers on a survey do not reflect the true feelings of the respondent.
Three different ways this can occur:
Interviewer Error
Misrepresented Answers
Wording of Questions
Ordering of Questions or Words
Type of Question
Data Entry Error

10. Types of Questions
Open-ended Questions
Close-ended Questions

11. Open-Ended Questions
What were the most important wars fought in the history of the United States?
What are you planning to buy today at the supermarket?
How exactly did the fight between the two of you start?
What is your favorite memory from childhood?
What do you plan to do immediately following graduation from college?
What types of decorations do you plan to have for your friend's birthday party?
What was your high school experience like?
How did you and your best friend meet?

12. Close-Ended Questions
May I use the bathroom?
Is the prime rib a special tonight?
Did that man walk by the house before?
Can I help you with that?
May I please have a bite of that pie?
Would you like to go to the movies tonight?
Is math your favorite subject?
Does four plus four equal eight?

13. Sampling Error versus Nonsampling Error
Nonsampling Errors are errors that result from undercoverage, nonresponse bias, response bias, or data-entry. Such errors could also be present in a complete census of the population.
Sampling Errors are the errors that result from using a sample to estimate information about a population. This type of error occurs because a sample gives incomplete information about a population.