Algebra I Chapter 12.1 Samples and Studies
Sampling Population: The entire group Sample: The group being studied
Systematic Sampling Members are selected according to a specified pattern. Example:
Self-Selected Sample Members volunteer to participate in the study. Example:
Convenience Sample Members are selected because they are easy to reach. Example:
Stratified Sample Members of a population are divided into distinct subgroups. Then, members are selected at random from each group. Example:
Turn and Talk Which of these methods of sampling seems the best to you? Why? Which of these methods seems problematic? Why?
Example 1: Identify the sample and the population. Then determine if the sample is random, self-selected, convenience, or stratified. Students at AHS are listed alphabetically. Every fourth student on the list is selected to participate in a study on lunch food.
Example 2: Identify the sample and the population. Then determine if the sample is random, self-selected, convenience, or stratified. Animals at a zoo are divided into groups based on their species. Random animals are then selected from each group to have their blood tested.
Example 3: Identify the sample and the population. Then determine if the sample is random, self-selected, convenience, or stratified. A manager at a supermarket polls the people who come into his store on their eating habits.
Bias An error that results in the misrepresentation of a population.
Example 1: Determine if each sample is biased or unbiased. Explain your decisions. A student polls members of student council to learn more about levels of student involvement at AHS.
Example 2: Determine if each sample is biased or unbiased. Explain your decisions. A blogger asks people at a country music festival what their favorite radio station is.
Example 3: Determine if each sample is biased or unbiased. Explain your decisions. A journalist surveys members of a Young Democrats group to learn more about the political opinions of young voters.
Types of Studies Name Description Example Census Survey Observational Study Experiment
Example 1 Determine if each scenario is a census, survey, observational study, or experiment. A company shows five different commercials to students, and records their reactions.
Example 2 Determine if each scenario is a census, survey, observational study, or experiment. A school polls their students about the types of food they would like to see in their cafeteria. Every third student receives a questionnaire.
Example 3 Determine if each scenario is a census, survey, observational study, or experiment. All American citizens respond to a questionnaire regarding household income.
Example 4 Determine if each scenario is a census, survey, observational study, or experiment. A research group wants to learn how rats react to different diets.
Questioning Survey questions must not be biased. Errors in questioning are made when questions: - are confusing - encourage answering in a certain way - cause a strong reaction - address more than one issue at a time
Example 1 Determine if each question is biased or unbiased. Explain your decisions. Is your favorite flavor of ice cream vanilla or delicious chocolate?
Example 2 Determine if each question is biased or unbiased. Explain your decisions. Don’t you think that Obama is a great president?
Example 3 Determine if each question is biased or unbiased. Explain your decisions. What do you eat for breakfast?
Example 4 Determine if each question is biased or unbiased. Explain your decisions. Do you like animals, and would you rather have a dog or a cat?