1. Among a sample of 1500 undergraduates, the average GPA was 3.2 (standard deviation 0.78). Construct and interpret a 95% confidence level for the true population mean GPA.

2. Among a sample of 387 adolescent women, the average relationship length 8.93 weeks (standard deviation 1.78). Construct and interpret a 99% confidence level for the true population mean relationship length.

3. Using the 2006 General Social Survey, in SPSS:

a) Construct and interpret a 95% confidence interval for the true mean years of education [educ], overall and controlling for gender.

b) Construct and interpret a 99% confidence interval for the true mean age when first married [agewed], overall and controlling for gender.