Suppose in a large class, students' grades in a test followed the normal distribution. Approximately what percent of grades are between two standard deviations below the mean and two standard...

Suppose in a large class, students' grades in a test followed the normal distribution. Approximately what percent of grades are between two standard deviations below the mean and two standard deviations above the mean? (that is in between Xbar-2S and Xbar+2S grades). Note, Xbar is the mean, and S is the standard deviation.

1. 34.3


2. 47.9


3. 95.8