新GRE数学考试其实主要是考察考生基础知识的掌握程度,当然不会考直接的概念,会结合数字进行考察。数理统计方面知识点如下:
众数
一组数中出现频率最高的一个或几个数。
例:mode of 1,1,1,2,3,0,0,0,5 is 1 and 0。
值域
一组数中最大和最小数之差。
例:range of 1,1,2,3,5 is 5-1=4
平均数 算术平均数
几何平均数
n个数之积的n次方根。
中数
对一组数进行排序后,正中间的一个数, 或者中间两个数的平均数。例: median of 1,7,4,9,2,5,8 is 5 median of 1,7,4,9,2,5 is /2=6
ps:GRE经常考察众数与数的个数的积和这组数的和的大小。
标准偏差
一组数中,每个数与平均数的差的绝对值之和,再除以这组数的个数n
例:standard error of 0,2,5,7,6 is: /5=2.4
standard variation
一组数中,每个数与平均数之差的平方和,再除以这组数的个数n
例: standard variation of 0,2,5,7,6 is: _ 2 2 2 2 2_
|_ ++++_|/5=6.8
标准偏差
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。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。
几个GRE最常用的概念:
偶数:能被2整除的整数;
奇数:不能被2整除的数;
质数:大于1的整数,除了1和它本身外,不能被其他正整数所整除的,称为质数。也叫素数;
倒数:一个不为零的数为x,则它的倒数为1/x。
最重要的性质:
奇偶性:偶加偶为偶,偶减偶为偶,偶乘偶为偶;
奇加奇为偶,奇减奇为偶,奇乘奇为偶;
奇加偶为偶,奇减偶为偶,奇乘偶为偶。
等差数列:新GRE数学中绝大部分是等差数列, 形式主要为应用题。题目会说三年稳步增长第一年的产量是x,第三年的产量是y,问你的二年的产量。
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