Homework Log Thurs 5/26 Lesson 11 – 8 Learning Objective: To analyze sampling methods and bias Hw: Pg. 729 #6-13 all, 15-19 odd

5/26/16 Lesson 11-8 Samples & Surveys Algebra II

Learning Objective To analyze sample To conduct surveys

Sample & Surveys Population – all members of a set Sample – part of a population Convenience Sample – select any members of the population who are conveniently & readily available. Self Selected Sample – select only members of the population who volunteer for the sample

Sample & Surveys Systematic Sample – order the population in some way, and then select from it at regular intervals Random Sample – all members of the population are equally likely to be chosen Bias – systematic error introduced by the sampling method Census– pool of every person in the population

Analyze Sampling Methods A newspaper wants to find out what percent of the city population favors a property tax increase to raise money for local parks. a.) What is the sampling method used for each situation? b) Does the sample have bias? Explain. 1. A newspaper article on the tax increase invites readers to express their opinions on the newspaper’s website. a. Self Selected Sample b. Has bias. Certain audiences

Analyze Sampling Methods A newspaper wants to find out what percent of the city population favors a property tax increase to raise money for local parks. a.) What is the sampling method used for each situation? b) Does the sample have bias? Explain. 2. A reporter interviews people leaving the city’s largest park. a. Convenience Sample b. Has bias. Only get people that go to parks

Analyze Sampling Methods A newspaper wants to find out what percent of the city population favors a property tax increase to raise money for local parks. a.) What is the sampling method used for each situation? b) Does the sample have bias? Explain. 3. A survey service calls every 50th listing from the local phone book. a. Systematic Sample b. Has bias. May have link between people listed & people that pay prop tax

Analyze Sampling Methods a.) What is the sampling method used for each situation? b) Does the sample have bias? Explain. 4. To survey the eating habits of the community, employees of a local t.v. station interview people visiting a food court in the mall. a. Convenience Sample b. Has bias. Over represent people that eat fast food

Analyze Sampling Methods 5. What situation requires a census instead of a sample? Population data for the US Population

Sample & Surveys Observational Study – you measure or observe members of a sample in such a way that they are not affected by the study Controlled Experiment – you divide the sample into two groups. Impose a treatment on one group but not on the other “control” group. & compare the effect on each group

Sample & Surveys Survey – you ask every member of the sample a set of questions ***A poorly designed study can result in unreliable statistics. You should always analyze a study’s methods before making general conclusions about the population.

Analyze Sampling Methods a) Which type of study method is described in each situation? b) Should the sample statistics be used to make a general conclusion about the population? 6. Researchers randomly choose two groups from 10 volunteers. Over a period of 8 weeks, one group eats ice cream before going to sleep, the other does not. Volunteers wear monitoring devices while sleeping, and researchers record dream activity. a. Controlled Experiment b. Sample is too small

Analyze Sampling Methods a) Which type of study method is described in each situation? b) Should the sample statistics be used to make a general conclusion about the population? 7. Students in a science class record the height of bean plants as they grow. a. Observational Study b. General conclusion, but soil type & amount of sunlight/water/other factors could affect the growth rate

Analyze Sampling Methods a) Which type of study method is described in each situation? b) Should the sample statistics be used to make a general conclusion about the population? 8. Student council members ask every tenth student in the lunch line if they like the cafeteria food. a. Survey b. Not reliable. People in line like cafeteria food versus those who brought lunch

Designing a Survey b. Usually least bias. “Who is pictured?” 9. During the 2008 Olympic Games, a U.S. swimmer won more medals than any other swimmer in history. a) What sampling method could you use to find the percent of students in your school who recognize that swimmer form a photograph? b) What is an example of a survey question that is likely to yield information that has no bias? a. Every 10th student entering school in the morning b. Usually least bias. “Who is pictured?”