Lesson 11.3 Collecting Data - Sampling Methods (Day 1) Learning Goal: (S-IC.A.1) I can identify types of sampling methods in statistical studies. I can recognize and explain biased samples. Essential Question: Why are there different sampling methods and what makes a sample biased? Homework Discussion

Identifying Sampling Methods in Statistical Studies Steps in a typical statistical study: Identify the variable of interest and the population of study. Choose a sample that is representative of the population. random sample - each member of population has an equal chance of being selected Collect data. types of samples: self-selected, systematic, stratified, cluster, convenience Organize and describe the data using a statistic. Interpret the data, make inferences, and draw conclusions about the population. (like new school logo) (HHS students) (100 HHS students) (data display) (mean, st. dev., IQR)

Examples: You want to determine whether students in your school like the new school logo. Identify the type of sample described. a. You list all of the students alphabetically and choose every sixth student. b. You mail questionnaires and use only the questionnaires that are returned. c. You ask all of the students in your algebra class. d. You randomly select two students from each classroom. e. You divide the students in your school according to their zip codes, then select all of the students that live in one zip code. Which of the above sampling methods do you think would be most representative of the population?

Group Consensus A student council wants to know whether students would like the council to sponsor a mid-winter dance or a mid-winter carnival this year. Classify each sampling method. a. Survey every tenth student on the school’s roster. b. Survey all students in three randomly selected homerooms. c. Survey 20 randomly selected freshmen, 20 randomly selected sophomores, 20 randomly selected juniors, and 20 randomly selected seniors. d. Survey those who ask the council president for a questionnaire. e. Survey a random selection of those who happen to be in the cafeteria at noon. Cluster Convenience Self-Selected Stratified Systematic

Recognize Bias in Sampling Bias - an error that results in a misrepresentation of a population Unbiased Sample - representative of the population that you want information about Biased Sample - a sample that over-represents or under-represents part of the population results in invalid data Examples: Identify the type of sample and explain why the sample is biased. a. A news organization asks its viewers to participate in an online poll about bullying. b. A computer science teacher wants to know how students at a school most often access the Internet. The teacher asks students in one of the computer science classes.

Group Consensus Identify the type of sample and explain why the sample is biased. a. The principal asks students at one lunch table about the quality of food served in the school's cafeteria. b. A sports announcer wants to know how often people in the town attend community sporting events. She asks every tenth person in attendance at a local soccer game.

Selecting an Unbiased Sample You are a member of your school’s yearbook committee. You want to poll members of the senior class to find out what the theme of the yearbook should be. There are 246 students in the senior class. Describe a method for selecting a random sample of 50 seniors to poll.

Practice to Strengthen Understanding Exit Ticket: The manager of a concert hall wants to know how often people in the community attend concerts. The manager asks 45 people standing in line for a rock concert how many concerts they attend per year. Identify the type of sample the manager is using and explain why the sample is biased. Practice to Strengthen Understanding HW #24 BI 614 #5-20