1. Bias Sampling

2. 2 Terminology Population: group about which information is desired. Sample: smaller group of people Random: Sample: everyone gets an equal chance of being selected

3. Bias Sample Not Fair Look For: 1.Sample is too small 2.Excludes part of the population 3.Includes groups outside of the population 3

4. Practice Tim’s middle school is from grades 6-8. Tim is conducting a survey about the sixth grade class trip. He wants to see if students would like to go to Shiloh National Military Park or the Grand Old Opry. Tim surveys students that are in the school band and the chorus. Is this sample bias? Explain. 4

5. Practice Carolyn wants to survey the adults in her town to see if there is interest in building a skateboarding park. What is the population of Carolyn’s survey? A.AdultsC. Skateboard fans B.Students D. The people who would use the park. 5

6. Practice Carolyn wants to survey the adults in her town to see if there is interest in building a skateboarding park. Which is the best sample for her survey? A.Survey all of the people that Carolyn sees skateboarding on Monday. B.Survey 50 students at random from Carolyn’s school/ C.Survey every hundredth name from the phone book. D.Survey the first 50 people that leave the mall. 6

7. Practice The sixth grade fall class trip will be either to a football game or Graceland. The sixth grade teachers are conducting a survey to see where their students want to go. Which survey is most likely to provide a bias sample? A.Survey all 6 th grade students. B.Survey every fifth 6 th grade student that arrives to school Friday morning. C.Survey fifty 6 th grade students whose names are picked out of a hat at random. D.Survey those students that play on a football team. 7

8. Exit Question A town mayor wants to know if the residents of a town are in favor of building a new football stadium. On Saturday, he randomly surveyed 50 male residents of the town to see if they were in favor of the new stadium. Which sentence best explains why this sample may be biased? A.The sample was taken on only one day. B.The sample included only males in the survey. C.The sample included residents of only one town. D.The sample did not include all the males in the town. 8

9. Practice You want to conduct a survey to find out which video game is the favorite of sixth grade students at your school. Which method would give you the best information of the survey? A.Call five of your friends. B.Randomly survey about 25% of the sixth grade students at your school. C.Randomly survey 6 th grade teachers. D.Choose your favorite games to be included in a survey. 9

10. Practice Jamal is conducting a survey to determine the average amount of time students spend on homework per week. Which of these does NOT represent a biased sample of students? A.The students who made the honor roll every grading period last year. B.Five students chosen randomly from every slot each class. C.Ten students sitting at a lunch table together. D.Twenty students at an afternoon baseball practice. 10

11. Practice Suzanne wants to conduct a survey about favorite hobbies. In order to have a NON- BIASED sample, she interviews people leaving the _____. A.Race track B.Fabric store C.Grocery store D.Football stadium 11

12. Practice Alyssa’s 6 th grade class is taking a survey of their favorite sports. There are 25 students in the class. Which of the following sample methods would NOT be biased? A.Randomly survey all the students in the class B.Randomly survey all the boys in the class C.Randomly survey all the girls in the class D.Randomly survey only the students that play sports. 12

13. Practice Sarah must collect data to create a bar graph. She wants to find out what kind of movies middle school students prefer. How should she collect her data to get an unbiased sample? A.Ask every tenth student in her grade level B.Ask everyone in line for the latest movie on Saturday night. C.Ask all her friends D.Ask every tenth student who enters the school building in the morning. 13

14. Practice You want to know which snack foods the students at your middle school prefer. Which of the following choices represent a random sample? A.All 6 th grade students in the school. B.7 th grade Social Studies teachers. C.Twenty 10 th grade students from the Science Club D.Select every 10 th student on your school roster. 14

15. Practice Which of the following would NOT give a bias sample? A.Asking teenagers at a mall their favorite place to shop. B.Asking teenagers at the movies what type of entertainment is their favorite. C.Asking teenagers exiting school their favorite actor. D.Asking teenagers at a basketball game their favorite athlete. 15

16. TCAP Bias Sampling Questions #22: Mr. Hansen is conducting a survey to determine how well the new mayor of a town is doing her job. Which group can Mr. Hansen use to produce results that are the LEAST biased? A.All the people who work for or who voted for the mayor. B.Fifty people chosen at random from each section of town. C.All the people in the town who volunteer at the high school and middle school. D.Fifty people who have recently written letters to the newspaper about the mayor. 16

17. TCAP Bias Sampling Questions #27: Mr. Villarreal wanted to determine if customers would like ice cream to be sold at his convenience store. He went to a nearby ice cream parlor and surveyed 75 people to determine if the customers at the parlor would be in favor of him selling ice cream at the convenience store. Which statement best explains why this sample group may be biased? A.The sample group had members who all came from one ice cream parlor. B.Those in the sample group are more likely to like ice cream. C.Those in the sample group are likely to have no opinion. D.The sample group had only 75 members. 17

18. TCAP Bias Sampling Questions #30: Ms. Ling conducted a survey to determine whether the price per gallon of gas influenced the type of transportation used by people in her town. She surveyed the driver of every fifth motorcycle coming into a gas station. Which statement is the most reasonable? A.Not Biased: Ms. Ling assumed the driver decided the mode of transportation that was used. B.Not Biased: Ms. Ling may not have surveyed an equal number of men and women. C.Biased: Ms. Ling’s survey of every 5 th driver was too random. D.Biased: Ms. Ling surveyed only people who used motorcycles. 18

19. Enrichment Bias Practice: Textbook Page AT6 Numbers: 6 and 7 Create a sample for the class to determine if bias or unbiased. Create a key with a justification of your answer. 19