Standard Deviation problems are RARELY encountered on the GMAT. You probably won't see one on your test--that's why most GMAT Math books don't even cover this topic.

Here's a link to introduce you to how Standard Deviation is calculated: https://coe.sdsu.edu/eet/Articles/standarddev/index.htm

Don't worry too much about these problems or spend too much time studying for them!

cooldude wrote:hey eric i came across them twice mean in each gmat prep :roll:

and people say bf cr question r hard and when u get it ur score is supposed to b good but man my very first question on verbal was bfcr

Even though you saw two standard deviation problems in your GMAT prep, I still would argue that you will not likely see these questions on your actual GMAT. That said, it still is a good idea to understand how to do them--but devote more time to mastering the fundamentals (arithmetic, alegebra, geometry) that will DEFINITELY be tested.

Your statement about boldface questions is a myth. Boldface questions vary in difficulty, just like any other verbal question. Try not to read too much into your performance if you encounter an boldface question early or late in your verbal section.

Best of luck to you!