新GRE数学考点标准偏差和排列组合GRE数学

1、智课网GRE备考资料新GRE数学考点 标准偏差和排列组合_GRE数学 新GRE数学考试的考点有很多，标准偏差和排列组合是其中的两个考点，为了帮助大家更好的掌握这两个考点，下面小编就给大家简单解析一下这两个新GRE数学的考点。 本文为大家介绍了新GRE数学考试中标准偏差和排列组合的相关内容,希望对大家备考新GRE数学有一定的参考作用！ 一、新GRE考试数学考点简析之标准偏差(standard deviation) standard deviation等于standard variation的平方根 GRE经常让你比较众数或中数与数的个数的乘积和这组数的和的大小，可以举几个极限情况的例子验证一下。

2、还有一种题型是给你两组数的平均值，方差，比较他们的中数大小;要注意中数的大小和那两个值是没有必然联系的，无法比较。 二、新GRE考试数学考点简析之排列组合 Set A set is a collection of objects or things. Each object in a set a member or element of that set.Size of a set is the number of members in the set. Example: The set of even numbers between 2 and 10 is of size 5:2,4,6,8

3、,10. The set of primes between 2 and 10 is of size 4:2,3,5,7. Remember: Each member of set A belongs to A or is in the set A. A set can not have repeating member:1,3,1,2is not a set. Rearranging the order of the members does not change the set:1,2,3is same as3,2,1. Combinations Number of ways we can

4、 select n objects from a group of m distinct objects is m!/(n!*(m-n)!). Example: Number of possible ways to pick 4 oscar nominations from a list of 50 movies is 50!/(4!*(50-4)!)=50!/(4!*46!)=50*49*48*47/24=230300. Remember: This does not apply if there are identical objects. Permutation of Objects The number of ways n distinct objects can be ordered is n!. Example: Number of ways 6 people can from a queue is 6!. Number of ways 5 different cars can be parked in 5 parking spaces is 5!. Remember: This d