Do Now

1. Do Now • There is 8 seconds left in the big game. Your team just scored a touchdown to bring the score to 26-27. Should you just kick the extra point and almost certainly go into overtime, or go for the two point conversion?

2. Objectives • 24.February.2011 • Students will be able to… • Define outcome bias. • Define sampling bias.

3. Agenda • Do Now (5 min) • Outcome Bias (10 min) • Sampling Bias (10 min) • Exit Ticket (5 min)

4. Outcome Bias • Outcome bias happens when a decision is based on its result after the fact and not on its merit at the time.

5. Sampling Bias • Sampling Bias occurs when segments of a population are less likely to be chosen than others. • There are a lot of ways we can have sampling bias.

6. Sampling Bias • Self-Selection Sample – biased because the people who would not volunteer for a survey are different than people who would. • The Caveman Effect – cave paintings have been found in France that date back 40,000. Of course, paintings not in caves the same age, would probably have been destroyed by erosion. But because these cave paintings survived, our ideas about early humans are cavemen.

7. Dewey Defeats Truman • The Chicago Tribune did a phone poll to determine the winner of the election… not realizing that not everyone had phones, and the ones that didn’t mostly voted Truman.

8. Homework • Read the selection from How to Lie with Statistics by Darrell Huff. • Write down five different examples of sampling bias in the writing.