alltimeacheiver wrote:I have seen this question In Princeton Review mannual Pls advcice on same. Or let me know if it is requeired to ignore.
You definitely do not need to know about normal distributions for the GMAT.
For standard deviation, all you need to know is in general what it means and, for data sufficiency, what's required to calculate SD. You'll never have to actually calculate it on test day (so you don't need the formula).
For DS purposes, to calculate standard deviation you need:
1) the number of terms; and
2) the exact spacing of the set.
Of course, if you know all of the terms in a set, you have both (1) and (2).
The general information to remember for the GMAT:
1) SD measures how spread out the terms in the set are from the mean;
2) the higher the SD, the more spread out the set from the mean; the lower the SD, the tighter packed the set is around the mean; and
3) when comparing graphs, assuming that the scales are the same, a flatter curve means a higher standard deviation and a steeper curve means a lower standard deviation.
While the above is somewhat simplistic, it's good enough for GMAT purposes.
