1. Lesson 8-7 Using Sampling to Predict

2. Definitions Sample - A small group, it is representative of a larger group, called a population.

3. Definitions Unbiased sample - selected so that it is representative of the entire population. TypeDefinitionExample Simple Random Sample A sample where each item or person in the population is as likely to be chosen as any other. The names of all students are put into a hat and drawn blindly. 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 item or people are selected according to a specific time or item interval. From an alphabetical list of all students attending a school, every 20th person is chosen.

4. Definitions Biased sample - One or more parts of a population are favored over others. TypeDefinitionExample Convenience Sample A convenience sample includes members of a population that are easily accessed. To represent all students in the school, the principal surveys one math class. Voluntary Response Sample A 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.

6. To determine which school lunches students like most, every twentieth student to walk into the cafeteria is surveyed. Describe each sample To determine what sports teenagers like, the student athletes on the girls’ field hockey team are surveyed. Unbiased – systematic random sample Biased – convenience sample

8. 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. Book TypesNumber of Students Mystery12 Adventure Novel 9 Sports11 Short Stories8 What percent of the students prefer mysteries? If 220 books are to be sold at the book fair, how many should be mysteries?