1. For a random sample of 150 students, the mean cost for textbooks during the first semester of college was found to be $370.75, and the sample standard deviation was $36.51. Assuming that the population is normally distributed, find the margin of error of a 95% confidence interval for the population mean.

3. Suppose that a random sample of156 graduate-admissions personnel was asked what role scores on standardized tests play in consideration of a candidate for graduate school. Of these sample members,

94 answered "very important." Find a 95% confidence interval for the population proportion of graduate admissions personnel with this view.

4. Compute the variance and standard deviation of the sample data shown below. 6 4 8 7 9 4 11