1. Math III U9D5 Warm-up: 1. Decide which method of data collection you would use to collect data for the study (observational study, experiment, simulation, or survey): a) A study of the salaries of college professors in a particular state b) A study where a political pollster wishes to know if his candidate is leading in the polls. c) A study where you would like to determine the chance getting three girls in a family of three children. d) A study of the effects of a fertilizer on a soybean crop e) A study of the effect of koalas on Florida ecosystem a) Survey b) Observation c) Simulation d) Experiment e) Simulation COLLECT TEST CORRECTIONS

2. HW Check pp. 19

3. HW Check pp. 20

4. HW Check pp. 22

5. HW Check pp. 23

6. M3U9D6 Bias Objective: Identify types of bias that might be present and write appropriate, non- biased questions to gather data.

7. Types of Bias: 1. Question wording bias – wording is confusing or misleading 2. Undercoverage bias – the population is not accurately represented in the sample 3. Response bias – people give false or misleading answers to questions 4. Nonresponse bias – people refuse to respond to survey 5. Voluntary response bias – people are asked to call in or respond to a survey by mail

8. WHAT TYPE OF BIAS DO YOU SEE? Ex 1: On the twelfth anniversary of the death of Elvis Presley, a Dallas record company sponsored a national call-in survey. Listeners of over 1000 radio stations were asked to call a 1-900 number (at a charge of $2.50) to voice an opinion concerning whether or not Elvis was really dead. It turned out that 56% of the callers felt Elvis was alive. Voluntary Bias

9. WHAT TYPE OF BIAS DO YOU SEE? Ex 2: In 1936, Literary Digest magazine conducted the most extensive (to that date) public opinion poll in history. They mailed out questionnaires to over 10 million people whose names and addresses they had obtained from telephone books and vehicle registration lists. More than 2.4 million people responded, with 57% indicating that they would vote for Republican Alf Landon in the upcoming Presidential election. Incumbent Democrat Franklin Roosevelt won the election, carrying 63% of the popular vote. Undercoverage Bias

10. Now you try… WHAT TYPE OF BIAS DO YOU SEE? Reword the statement so it is not biased. 1. Do you think the city should risk an increase in pollution by allowing expansion of the Northern Industrial Park? 2. If you found a wallet with $100 in it on the street, would you do the honest thing and return it to the person or would you keep it? Should the city allow for expansion of the Northern Industrial Park? What would you do if you found a wallet on the street?

11. Here are some types of bias and a brief explanation of each: Deliberate bias: Here is a question asked in two ways, one to try to remain unbiased and one to be deliberately biased. 1. If you found a wallet with $100 in it on the street, would you keep it? 2. If you found a wallet with $100 in it on the street, would you do the honest thing and return it to the person or would you keep it? Unintentional bias: Words mean different things in different contexts and to different people. For example: 1. Over the last few years, have you watched a lot of television? 2. In the last two years, have you watched more than 4 hours of television daily, on average? Question 2 avoids the terms "few" and "a lot" which may have different meanings to different people. Unnecessary complexity: Sometimes questions ask more than one question or are worded in a confusing way. For example, you could ask: "How do you feel about the ticket price and the stadium condition for varsity football?" What if they feel the ticket price is too much but think the stadium is fine? This needs to be two distinct questions. Ordering of questions: The manner in which questions are ordered can create problems for two reasons. First, earlier questions can bring to mind issues that might not otherwise be on the mind of the respondent. Second, sometimes respondents think one question is supposed to apply to the previous one.

12. Sampling Bias

14. Classwork: Bias or Unbiased Survey Questions pp. 24 Homework: Statistics Review pp. 25-26