2015年GMAT數學基本概念解讀：統計

　　在GMAT數學的備考過程當中，對根本數學觀點的懂得和影象很主要，在GMAT測驗的過程當中，會出項一些關於GMAT數學統計的題目，下面便是存眷這些題目標一些常見統計觀點，供眾人參考。

　　gmat數學備考之描寫統計(descriptive statistics)

　　1.均勻數(average or arithmetic mean)

　　2.中數(median)

　　To calculate the median of n numbers，first order the numbers from least to greatest;if n is odd，the median is defined as the middle number，while if n is even，the median is defined as the average of the two middle numbers. For the data 6, 4, 7, 10, 4, the numbers, in order, are 4, 4, 6, 7, 10, and the median is 6, the middle number. For the numbers 4, 6, 6, 8, 9, 12, the median is (6+8 )/2 = 7. Note that the mean of these numbers is 7.5.

　　3.眾數(mode)：一組數中的眾數是指湧現頻率最高的數。

　　例：the mode of 7，9，6，7，2，1 is 7。

　　4.值域(range)：註解數的散布的量，其被界說為最大值減最小值的差。

　　例：the range of–1，7，27，27，36 is 36-(-1)= 37。

　　5.尺度方差(standard deviation)：

　　One of the most common measures of dispersion is the standard deviation. Generally speaking, the greater the data are spread away from the mean, the greater the standard deviation. The standard deviation of n numbers can be calculated as follows:

　　(1)find the arithmetic mean ;

　　(2)find the differences between the mean and each of the n numbers ;

　　(3)square each of the differences ;

　　(4)find the average of the squared differences ;

　　(5)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.

　　GMAT數學的根本觀點，假如考生加以歸類，會感到沒有想象中那末龐雜和淩亂。考生可以依據歸類的GMAT數學根本觀點，加以溫習和影象。還要提示考生的是，GMAT數學的根本觀點，最隱諱的是死記硬背，考生最佳采取懂得式影象法，GMAT數學根本觀點就可以輕松搞定。