Sampling Distributions 2-2 This content begins on page 44 of a book that is on a truck that is on it’s way to Lassiter.

Simple Random Sample Members are chosen using a method that gives everyone an equally likely chance of being selected. Systematic Sample Members are chosen using a pattern, such as selecting every other person. Stratified Sample The population is first divided into groups. Then members are randomly chosen from each group. Cluster Sample The population is first divided into groups. A sample of the groups is randomly chosen. All members of the chosen groups are surveyed. Convenience Sample Members are chosen because they are easily accessible. Self-Selected Sample Members volunteer to participate.

Example 1 Classifying a Sample The officials of the National Football League (NFL) want to know how the players feel about some proposed changes to the NFL rules. They decide to ask a sample of about 100 players. Classify each sample.

Simple Random Sample Systematic Sample Stratified Sample Cluster Sample Convenience Sample Self-Selected Sample The officials choose the first 100 players who volunteer their opinions. This is a self-selected sample because the players volunteer.

Simple Random Sample Systematic Sample Stratified Sample Cluster Sample Convenience Sample Self-Selected Sample The officials randomly choose 3 players from each of the 32 teams in the NFL. This is a stratified sample because the players are separated by team and randomly chosen from each team.

Simple Random Sample Systematic Sample Stratified Sample Cluster Sample Convenience Sample Self-Selected Sample The officials have a computer generate a list of 100 players from a database that includes all of the players in the NFL. This is a simple random sample because each player (and each permutation of 3 players) has an equal chance of being chosen.

Which Sampling Method is the Best? Most Accurate – census Very Accurate – simple random sample – stratified sample – cluster sample Not Very Accurate – convenience sample – self-selected sample Simple Random Sample Self-Selected Sample Systematic Sample Stratified Sample Cluster Sample Convenience Sample

Example 2 Evaluating Sampling Methods A high school has 552 freshmen, 495 sophomores, 449 juniors, and 439 seniors enrolled. The student newspaper wants to take a survey of the school. Classify each sampling method. Which is most accurate? Which is least accurate? Explain your reasoning.

Example 2 Classify each sampling method. Which is most accurate? A high school has 552 freshmen, 495 sophomores, 449 juniors, and 439 seniors enrolled. Method A Randomly select 50 freshmen, 50 sophomores, 50 juniors, and 50 seniors from the complete roster. Method B Randomly select 200 students from the complete roster. Method C Choose every 10th student who enters the cafeteria at lunchtime. Stratified Sample Simple Random Sample Systematic Sample Most Accurate Least Accurate Middlest Accurate

2. A small-town newspaper wants to report on public opinion about the new City Hall building. Classify each sampling method. Which is most accurate? Which is least accurate? Method A Ask readers to write in and give their opinion. Method B Survey 10 randomly selected female students and 10 randomly selected male students in the cafeteria during the lunch period. Method C Randomly choose 10 streets in the town and survey everyone who lives on each street. Self Selected Convenience Sample Cluster Sample Most Accurate Least Accurate Not as bad as A

School start time to move to 10:00 AM starting October 1 st. Students at a high school will vote on a proposal to start classes later in the day. According to a survey of a random sample of students, 54% of the students agree with the proposal and 46% of the students disagree with the proposal. The survey’s margin of error is ±5%. Does the survey clearly project the outcome of the voting?

Do we have a winner? A survey of a random sample of voters shows that 38% of voters plan to vote for Gonzalez, 31% of voters plan to vote for Chang, and 31% plan to vote for Harris. The survey has a margin of error of ±3%. Does the survey clearly project the outcome of the voting? Explain.

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