ETS GRE Quantitative Practice book pg. 145 #15
In my most liked YouTube math video below, I explain an official ETS quant question that involves the concepts of standard deviation and normal distribution. If you're like me, you didn't learn these in high school math class, so I explain them like you're six years old, or more accurately, like you're 23 with the math skills of a six-year-old. :)
The good news is we don't have to actually calculate standard deviation on the GRE - we just have to understand the basics about the concept to get this question right.
If you liked this video, check out my other free GRE resources.