The U. S. Department of Education reported that in 2007, 67% of students enrolled in college or a trade school within 12 months of graduating from high school. In 2013, a random sample of 160 individuals who graduated from high school 12 months prior was selected. From this sample, 102 students were found to be enrolled in college or a trade school.

a. Construct a 90% confidence interval to estimate the actual proportion of students enrolled in college or a trade school within 12 months of graduating from high school in 2013.

b. What is the margin of error for this sample?

c. Based on this sample, is there any evidence that this proportion has changed since 2007?

d. Verify your results with PHStat.