find the arithmetic mean ;
find the differences between the mean and each of the n numbers ;
square each of the differences ;
find the average of the squared differences ;
take the nonnegative square root of this average.
Notice that the standard deviation depends on every data value, although it depends most on values that are farthest from the mean. This is why a distribution with data grouped closely around the mean will have a smaller standard deviation than data spread far from the mean.
如果考生将GMAT数学概念加以归类,思路会更清晰。考生可以根据归类的GMAT数学概念加以复习。对于GMAT数学概念切莫死记硬背,在理解的基础进行记忆一方面是比较方便记忆,一方面还能真正理解单词的含义,提高准确性。
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