What is the mean number of hours that high school students spend on homework per week? It is known that the standard deviation of the population is 2.2 hours. In a random sample of 40 students, it is found that they average 13 hours per week on homework.

1. What is the standard deviation for this sample?
2. What is the critical value for a 90% confidence interval?
3. What is the critical value for a 95% confidence interval?
4. What is the 90% confidence interval? Be sure to include the formula with your numbers plugged in.
5. What is the 95% confidence interval?