1. What are the Z-scores for the following Confidence Intervals? Assume you are interested in both tails of the curve, positive and negative (3 points).

68% ___________________

50% ___________________

80% ___________________

1. Assume you had a random sample of 70 graduate students' GRE scores and you calculated a mean of 300 and standard deviation of 45. Using a confidence level of 90%, calculate and interpret the margin of error (2 points).

1. Assume that you have a random sample of 100 countries and you are interested in unemployment rates but you do not know the population parameters. Your sample mean is 6.7 and you sample standard deviation is 1.9. Complete the following:

1. What is your single best guess average employment rate of all the countries in the world?

1. Calculate the Confidence Interval (CI) at 90% confidence

1. Calculate CI at 95% confidence

1. Calculate CI at 99.7% confidence

1. Describe what happens to the confidence bounds as we increase the level of confidence. AKA are the bounds large for 95% or for 90%? Explain.

The 95 percent confidence interval for the population mean is 286.64 313.36, indicating that we are 95 percent certain that the interval contains the genuine population mean (286.64 , 313.36)