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6.4 Select and draw conclusions from samples

6.4 Select and draw conclusions from samples. GOAL: study different sampling methods for collecting data. Sample: subset of the population. Self-selected sample , members of a population can volunteer to be in the sample.

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6.4 Select and draw conclusions from samples

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  1. 6.4 Select and draw conclusions from samples GOAL: study different sampling methods for collecting data.

  2. Sample: subset of the population Self-selected sample, members of a population can volunteer to be in the sample. Systematic sample, a rule is used to select members of a population, such as selecting every other person. Convenience Sample, easy-to-reach members of a population are selected, such as those in the first row Random Sample, each member of a population has an equal chance of being selected

  3. Classify samples Example 1:A teacher wants to find out how many hours students studied for a history quiz. Identify the type of sample described. • Before leaving the room, the teacher asks students to write the number of hours they studied for the quiz on the chalkboard if they want to participate. • The teacher selects students randomly from an alphabetical list and asks the selected students how many hours they studied for the quiz. Self selected Sample Random Sample

  4. Biased vs Unbaised Overrepresent or Underrepresent the population Represents the population Tell whether each the following samples are biased or unbiased Example 2: • A teacher wants to find out how many hours students studied for a history quiz. • Before leaving the room, the teacher asks students to write the number of hours they studied for the quiz on the chalkboard if they want to participate. • The teacher selects students randomly from an alphabetical list and asks the selected students how many hours they studied for the quiz. Biased unBiased

  5. Margin of Error

  6. Example 3: In a survey of 800 people, 20% said they get a haircut once per month. • What is the margin of error for the survey? • Give an interval that is likely to contain the exact percent of all people who get a haircut once per month Between 16.5% and 23.5%

  7. You Try…… Convenience • An electronics company wants to know which aspect of their MP3 player is the consumers’ favorite. Technicians are required to ask the question to all customers calling for technical support. Identify the type of sample described. 2. Tell whether the sample in Exercise 1 is biased or unbiased. Explain. 3. In a survey of 1100 home buyers, 90% said they used a real-estate agent to research home listings. What is the margin or error? Give an interval that is likely to contain the exact percent of all home buyers who used a real-estate agent to research home listings. Biased Between 87% and 93%

  8. Problem Solving Workshop Workbook Page 258 1-24 Homework: Textbook Page 230: 1-17

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