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Samples, Surveys, and Identifying Bias Algebra A Unit 3, Lesson 9
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What is Sampling? video
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Definition: The population is the entire group of individuals about which we want information. A sample is the part of the population from which we actually collect information. We use information from a sample to draw conclusions about the entire population. Population Sample Collect data from a representative Sample... Make an Inference about the Population. www.basd.k12.wi.us/.../TPS4e_Ch4_4.1....
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Example: The cafeteria staff wants to know how many students in the school enjoy pizza for lunch. They send Mrs. King to ask a group of 40 students if they like the cafeteria pizza. What is the population? What is the sample?
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Three methods of sampling: 1. Random: Survey a population at random. 2. Systematic: Select a random number n and survey every nth person. 3. Stratified: Separate the population into smaller groups and survey a random sample in each group.
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Example: Of the 40 students surveyed, 28 state that they like the school’s pizza. If the school has 500 students that buy lunch, how many students should they expect to buy pizza?
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Definition: Choosing individuals who are easiest to reach results in a convenience sample. www.basd.k12.wi.us/.../TPS4e_Ch4_4.1.... Bad Samples: Definition: A voluntary response sample consists of people who choose themselves by responding to a general appeal.
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Bias… …in a survey question. “Do you prefer exciting action movies or studious documentaries?”
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Bias… …in survey results. A sports magazine sends out a survey to its subscribers asking them to identify their favorite sport. As incentive, anyone who responds will receive a free box of golf tees.
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