We want to estimate the mean change in scorein the population of all high school seniors. An SRS of 400 high school seniors gained an average ofx(bar)=25

points in their second attempt at the SAT Mathematics exam. Assume that the change in score has a Normal distribution with standard deviation 51.654.

Find x, the standard deviation of the mean change of x (bar). ___(0.001).

Using the 68-95-99.7 Rule (Empirical Rule), give a 95% confidence interval for based on this sample.

Confidence interval (0.001) is between____and____