1. Warm Up
A 2003 paper investigated the tendency of people to rationalize their poor performance. Subjects were initially given a test asking them to guess the emotion exhibited in a picture of a face they were shown. The results were ignored and subjects were randomly assigned to a group that was told they received an “A” on the test or a group that was told they received a “D” on the test. Subjects were then asked to rate from 1-10 the importance of face reading as a skill. Sample Size Mean Std Dev “A” Group “D” Group Is this convincing evidence that the “grades” affected the subjects’ rating of the importance of face reading as a skill?

2. Practice
Are young adults more likely than middle-aged adults to sleep with their cell phones? Assume that for a random sample of 258 adults in the age group 168 said they sleep with their cell phone. A random sample of 129 adults in the age group found that 61 said yes. Calculate the 90% confidence interval for the difference in the proportion of young adults who sleep with their cell phones vs. middle-aged adults.

3. Practice
A 2003 study by the Kaiser Family Foundation surveyed 200 randomly selected children aged 6 months to 3 years and found that 30% had a TV in their rooms. In addition they surveyed 200 randomly selected children aged 3 to 6 years old and found that 43% had a TV in their rooms. The two samples were taken independently. Construct a 95% confidence interval for the difference in the proportion of 3 to 6 year olds with a TV in their room vs. 6 months to 3 year olds with a TV in their room.

4. Is Flipping a Bent Coin Different from Flipping a Regular Coin?
You will be given either a bent penny or a regular penny. You will flip your coin 30 times and count the total number of heads. Let your coin hit the floor each time! Record the number of heads in the correct category on the board. We will construct a confidence interval for the difference of the proportions between the 2 populations. (Proportion bent – Proportion regular)

5. Is Flipping a Bent Coin Different from Flipping a Regular Coin?
1) Using the data from everyone in the class, construct a 90% confidence interval for the difference in the proportion of heads for a bent penny vs. a regular penny. 2) Is this convincing evidence that the bent penny is more likely to land heads up than a regular penny? Explain why or why not.