9-1 Samples and Surveys Warm Up Problem of the Day Lesson Presentation Course 3 Warm Up Problem of the Day Lesson Presentation

9-1 Samples and Surveys Warm Up Evaluate. 1. t + 15 for t = –5 Course 3 9-1 Samples and Surveys Warm Up Evaluate. 1. t + 15 for t = –5 2. n + (–13) for n = 7 Solve for x. 3. = –21 4. 7x = –98 10 –6 x –3 x = 63 x = –14

9-1 Samples and Surveys Problem of the Day Course 3 9-1 Samples and Surveys Problem of the Day Mr. Gray’s 29 students will be sitting in the gym to watch a play. There are two rows of five chairs, three rows of four chairs, and four rows of two chairs. Is there enough room for all the students to sit? yes

Course 3 9-1 Samples and Surveys Learn to identify sampling methods and to recognize biased samples.

Insert Lesson Title Here Course 3 9-1 Samples and Surveys Insert Lesson Title Here Vocabulary population sample random sample systematic sample stratified sample convenience sample voluntary-response sample biased sample

Course 3 9-1 Samples and Surveys A fitness magazine printed a readers’ survey. Statements 1, 2, and 3 are interpretations. Which do you think the magazine would use? 1. The average American exercises 3 time a week. 2. The average reader of this magazine exercises 3 time a week. 3. The average reader who responded to the survey exercises 3 time a week.

Course 3 9-1 Samples and Surveys The population is the entire group being studied. The sample is the part of the population being surveyed. A fitness magazine printed a readers’ survey. Statements 1, 2, and 3 are interpretations. Which do you think the magazine would use? To get accurate information, it is important to use a good sampling method. In a random sample, each member of the population has an equal chance of being selected. A random sample is best, but other methods can be used.

9-1 Samples and Surveys Sampling Method How Members are Chosen Random Course 3 9-1 Samples and Surveys Sampling Method How Members are Chosen Random By chance Systematic According to a rule or formula Stratified At random from randomly chosen subgroups Convenience Easiest to reach Voluntary-response Members choose to be in the sample

Additional Example 1A: Identifying Sampling Methods Course 3 9-1 Samples and Surveys Additional Example 1A: Identifying Sampling Methods Identify the sampling method used. In a county survey, Democratic Party members whose names begin with the letter D are chosen. systematic The rule is to survey members whose names begin with D.

Additional Example 1B: Identifying Sampling Methods Course 3 9-1 Samples and Surveys Additional Example 1B: Identifying Sampling Methods Identify the sampling method used. A telephone company randomly chooses customers to survey about its service. random Customers are chosen by chance.

Additional Example 1C: Identifying Sampling Methods Course 3 9-1 Samples and Surveys Additional Example 1C: Identifying Sampling Methods Identify the sampling method used. A high school randomly chooses three classes from each grade and then draws three random names from each class to poll about lunch menus. stratified The three classes are the random subgroups. Names are chosen randomly from within the classes.

9-1 Samples and Surveys Check It Out: Example 1A Course 3 9-1 Samples and Surveys Check It Out: Example 1A Identify the sampling method used. In a county survey, families with 3 or more children are chosen. systematic The rule is to survey families with 3 or more children.

9-1 Samples and Surveys Check It Out: Example 1B Course 3 9-1 Samples and Surveys Check It Out: Example 1B Identify the sampling method used. A retail home improvement store randomly selects customers to take a survey about their shopping experience. random Customers are chosen by chance.

9-1 Samples and Surveys Check It Out: Example 1C Course 3 9-1 Samples and Surveys Check It Out: Example 1C Identify the sampling method used. At a basketball game 5 sections are chosen at random and 20 people from each section are randomly polled. stratified The five sections are the random subgroups. 20 people are chosen randomly from within the sections.

Course 3 9-1 Samples and Surveys Sometimes, these sampling methods result in biased samples. A biased sample does not accurately represent the population. The data collected from biased samples is not reliable.

Additional Example 2A: Identifying Biased Samples Course 3 9-1 Samples and Surveys Additional Example 2A: Identifying Biased Samples Identify the population and the sample. Give a reason why the sample could be biased. A record store manager asks customers who make a purchase how many hours of music they listen to each day. Population Sample Possible Bias Customers who make a purchase might be more interested in music than others in the store. Customers who make a purchase. Record store customers.

Additional Example 2B: Identifying Biased Samples Course 3 9-1 Samples and Surveys Additional Example 2B: Identifying Biased Samples Identify the population and the sample. Give a reason why the sample could be biased. An eighth-grade student council member polls classmates about a new school mascot. Population Sample Possible Bias She polls more eighth-graders than students in other grades. Students in the school Classmates

Additional Example 2C: Identifying Biased Samples Course 3 9-1 Samples and Surveys Additional Example 2C: Identifying Biased Samples Identify the population and the sample. Give a reason why the sample could be biased. A radio DJ asks listeners for feedback about the type of music played on a radio show. Population Sample Possible Bias People who listen to the radio show People who hear the question and who call in The radio only receives feedback from people who listen to that station, and therefore who already enjoy the type of music played on the station.

9-1 Samples and Surveys Population Sample Possible Bias Course 3 9-1 Samples and Surveys Check It Out: Example 2A Identify the population and the sample. Give a reason why the sample could be biased. The first 5 people leaving a movie theater at a sneak preview were asked how they liked the movie. Population Sample Possible Bias People that really enjoy a movie are less likely to be one of the first ones to leave. People that went to the movie The first five people that left

9-1 Samples and Surveys Population Sample Possible Bias Course 3 9-1 Samples and Surveys Check It Out: Example 2B Identify the population and the sample. Give a reason why the sample could be biased. Eighth-grade students with a 3.0 GPA or higher were polled to determine how long students study each day. Population Sample Possible Bias Eighth grade students Students with 3.0 or higher GPA Students with lower grades are less likely to study as long.

9-1 Samples and Surveys Population Sample Possible Bias Course 3 9-1 Samples and Surveys Check It Out: Example 2C Identify the population and the sample. Give a reason why the sample could be biased. People attending a baseball game were asked if they support the construction of a new stadium in the city. Population Sample Possible Bias People that attend a baseball game are more likely to support the construction of a new stadium. City residents People attending a game

Insert Lesson Title Here Course 3 9-1 Samples and Surveys Insert Lesson Title Here Lesson Quiz: Part I Identify the population and sample. Give a reason why the sample could be biased. 1. A high school principal asks the first three people who leave the school play whether they liked it. Population Sample Possible Bias People that enjoy a play may not leave as early as someone who didn’t. People who attended the play The first 3 people leaving

Insert Lesson Title Here Course 3 9-1 Samples and Surveys Insert Lesson Title Here Lesson Quiz: Part II Identify the sampling method used. 2. At a baseball game, 10 sections are chosen at random and 10 random people from each section are polled. 3. A telemarketer calls the people that have a last name beginning with H. stratified systematic