GMAT Problem Solving (PS) | Re: The mean and the standard deviation of the 8 numbers shown

The phrase ' Within one standard deviation ' actually means the values which lie in the (10 - 0.3) and (10 + 0.3)
So we have see which values lie between 9.7 and 10.3
clearly 6 values from the given list lie within one standard deviation
percent of values which lie within one SD = \(\frac{6}{8}\) * 100 = 75%
correct answer - D

---