8-1 Random Samples and Surveys

Video Tutor Help Identifying a Random Sample Khan Academy

Video Tutor Help Identifying appropriate samples of a population Identifying bias in questions Estimating populations using capture/recapture

Worksheets Daily Notetaking Guide Worksheets Version A Practice, Guided Problem Solving Lesson 8-1 Practice 8-1 Guided Problem Solving 8-1

Vocabulary Practice Vocabulary 8A: Graphic Organizer Vocabulary 8B: Reading Comprehension Vocabulary 8C: Reading/Writing Math Symbols Vocabulary 8D: Visual Vocabulary Practice Vocabulary 8E: Vocabulary C Vocabulary 8F: Vocabulary Review Puzzle Vocabulary (Electronic) Flash Cards Measurement

Additional Lesson Examples Step-by-Step Examples Lesson 8-1

Lesson Readiness Lesson Quiz Problem of the Day Lesson 8-1

Sample: a randomly selected group chosen for the purpose of collecting data. Population: the entire group of items or individuals from which the samples under consideration are taken. Unbiased sample: is selected so that it is representative of the entire population.

Unbiased Samples TypeDefinition Example Simple random sample a sample where each item or person in the population is as likely to be chosen as any other Each student’s name is written on a piece of paper. The names are placed in a bowl, and names are picked without looking. Stratified random sample The population is divided into similar, non-overlapping groups. A simple random sample is then selected from each group. Students are picked at random from each grade level at a school. Systematic random sample. The items or people are selected according to a specific time or item interval. From an alphabetical list of all students attending a school, every 20 th person is chosen

Biased Sample In a biased sample, one or more parts of the population are favored over others.

Biased Sample TypeDefinitionExample Convenience SampleIncludes members of a population that are easily accessed. To represent all the students attending a school, the principal surveys the students in one math class. Voluntary response sample Involves only those who want to participate in the sampling. Students at a school who wish to express their opinion are asked to come to the office after school.

Example 7-1a To determine which school lunches students like most, every twentieth student to walk into the cafeteria is surveyed. Describe the sample. Answer: Since the population is the students entering the cafeteria, the sample is a systematic random sample. It is an unbiased sample. Describe Samples

Example 7-2a To determine what sports teenagers like, the student athletes on the girls’ field hockey team are surveyed. Describe the sample. Answer: Teenagers on the field hockey team are more likely to choose field hockey. This is a biased sample. The sample is a convenience sample because the people are easily accessed. Describe Samples

Example 7-3a BOOKS The student council is trying to decide what types of books to sell at its annual book fair to help raise money for the eighth-grade trip. It surveys 40 students at random. The books they prefer are in the table. What percent of the students prefer mysteries? 8short stories 11sports 9adventure novel 12mystery Number of Students Book Type Answer: 30% of the students prefer mysteries. 12 out of 40 students prefer mysteries. Using Sampling to Predict

Suppose you survey students in your school about their snacking habits. Would you get a random sample if you questioned different English classes? Explain. LESSON 8-1 Almost every student in the school is probably taking at least one English class. Random Samples and Surveys This sample is likely to be random. Additional Examples

It implies that pink is brighter, thus influencing the responses. Is each question biased or fair? Explain. LESSON 8-1 a. Which is a brighter color, pink or green? b. Is an electric pink shirt brighter than a green shirt? This question is biased. The choices are presented equally. This question is fair. Random Samples and Surveys Additional Examples