1. Lesson 12.8 Extension Populations and Samples
Essential Question: How do you identify biased samples and surveys?

2. Before we start… Have you ever conducted or been part of a survey?
Let’s survey the class…
“What is your favorite sport?”
“Don’t you think that watching a football game is more exciting than watching a tennis match?”

3. What is a survey?
The entire group you want information about is called a population.
Sometimes you survey a sample, which is a part of the population.
A study of one or more characteristics of a group.

4. Sample Sizes
The size of a sample affects the reliability of the results. Larger samples are considered to be more reliable because it decreases the chance of getting misleading results.

5. What sample should be used?
The best kind of sample to pick is a random sample.

6. What is a random sample?
Every member of the population has an equal chance of being selected.

7. Random Samples Represent the population as a whole
The inferences made based on the sample will also be true about the population

8. What is a biased sample?
A sample that’s not representative of the population. In this case some members of a population are more likely to be chosen than others.

9. What is a biased sample?
over-represented
under-represented

10. What is a biased question?
A question that encourages a particular response.
Survey questions should be worded to avoid bias.

11. Writing Survey Questions
When you create a survey, you need to phrase the questions so that the responses accurately reflect the views of the people surveyed.

12. How do you identify biased samples and surveys?
Consider who was selected to participate in the survey.
Consider how the questions were worded.

13. Nina wants to know how the students in her school feel about the new dress code. She randomly selects the names of 100 students from a school list and s each of them a survey. She waits for responses and records data from the surveys that are returned to her. Is her sample biased?

14. Consider this survey. Tripp wants to know how the students in his school feel about the new dress code. He surveys all the students in his homeroom. Is his survey biased? If it is, what could he have done differently to make it representative?

15. What if Tripp arrives at school early one morning and he surveys the first 50 students who arrive at school. Is this a good sample that is likely to be representative?

16. Roberto wants to know the favorite sport of adults in his hometown
Roberto wants to know the favorite sport of adults in his hometown. He surveys 50 adults at a baseball game. Is this sample biased?

17. Paula wants to know the favorite type of music for students at her school. She surveys the first 60 people who enter the school doors in the morning. Is this sample biased?

18. Is the question biased? Why? Rewrite any biased questions.
Don’t you agree that the voting age should be lowered to 16 because many 16-year-olds are responsible and informed?

19. Is the question biased? Why? Rewrite any biased questions.
Do you support the unfair policy of requiring students to do a time-consuming community project?

20. Is the question biased? Why? Rewrite any biased questions.
Do you support the incumbent’s tax plan or the challenger’s tax plan?

21. Is the question biased? Why? Rewrite any biased questions.
Do you like our new apple-nut yogurt flavor, now on sale in stores everywhere?

22. A researcher chose a random sample of registered voters in Kentsville
A researcher chose a random sample of registered voters in Kentsville. He found that 3 out of every 5 voters surveyed said they would vote for Miguel Miller for mayor. If there are 800 eligible voters in Kentsville, predict how many of those voters will choose Miguel Miller for mayor. Why would this be a valid inference to draw from these data?

23. Sarah randomly surveyed 80 students at her school
Sarah randomly surveyed 80 students at her school. She found that 15 out of the 80 students she surveyed chose pizza as their favorite school lunch option. If there are 700 students at her school, predict how many students at her school would choose pizza as their favorite lunch option. If the answer you get is a decimal, how do you interpret that?

24. How do you identify biased samples and surveys?

25. Ticket Out the Door
Is the question biased? Do you think filthy rich people should pay more in taxes?