1. According to USA Today, the average credit card debt for college senior is $3,262. If credit card debt is normally distributed with a standard deviation of $1,100. What is the probability that a randomly selected college senior owes more than $4,000?

2. According to the Chronicle of Higher Education, full-time Ph.D. students receive an average of $12,837 per year. If the average salary is normally distributed with a standard deviation of $1,500. Find the percentage of full-time Ph.D. students who makes more than $15,000 a year?

3. The national average for the number of students per teacher for all U.S. public schools is 15.9. A random sample of 12 school districts from a moderately populated area showed that the mean number of students per teacher was 19.2 with a standard deviation of 2.1. Find the 95% confidence interval of the true mean number of students per teacher.

4. A recent study showed that the modern working person experiences an average of 2.1 hours per day of distractions (phone calls, emails, ...). A random sample of 50 workers for a large corporation found that these workers were distracted an average of 1.8 hours per day and the population standard deviation was 20 minutes. Estimate the 99% confidence interval of the true mean population distraction time and compare your answer to the results of the study.

5. A health researcher claims that a 200-pound male can burn an average of 546 calories per hour playing tennis. Thirty-six males were randomly selected and tested. The mean number of calories burned per hour was 544.8. The population standard deviation is 3 and the P value is 0.0082. Test the claim that the average number of calories burned is actually less than 546. Use = 0.01.

6. According to the U.S. Bureau of Labor Statistics (BLS), a person between the ages of 18 and 34 has an average of 9.2 jobs. To see if this average is correct, a researcher selected a sample of 8 workers between the ages of 18 and 34 and asked how many different places they had worked. The results were as follows:

8 12 15 6 1 6 13 2

At 5% level of significance can it be concluded that the mean is 9.2? The P-value is 0.4872.