2015年GMAT數(shù)學(xué)基本概念解讀：統(tǒng)計(jì)

　　在GMAT數(shù)學(xué)的備考過(guò)程中，對(duì)基本數(shù)學(xué)概念的理解和記憶很重要，在GMAT考試的過(guò)程中，會(huì)出項(xiàng)一些關(guān)于GMAT數(shù)學(xué)統(tǒng)計(jì)的問(wèn)題，下面就是關(guān)注這些題目的一些常見(jiàn)統(tǒng)計(jì)概念，供大家參考。

　　gmat數(shù)學(xué)備考之描述統(tǒng)計(jì)(descriptive statistics)

　　1.平均數(shù)(average or arithmetic mean)

　　2.中數(shù)(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(shù)(mode)：一組數(shù)中的眾數(shù)是指出現(xiàn)頻率最高的數(shù)。

　　例：the mode of 7，9，6，7，2，1 is 7。

　　4.值域(range)：表明數(shù)的分布的量，其被定義為最大值減最小值的差。

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

　　5.標(biāo)準(zhǔn)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(shù)學(xué)的基本概念，如果考生加以歸類(lèi)，會(huì)感覺(jué)沒(méi)有想象中那么復(fù)雜和混亂?？忌梢愿鶕?jù)歸類(lèi)的GMAT數(shù)學(xué)基本概念，加以復(fù)習(xí)和記憶。還要提醒考生的是，GMAT數(shù)學(xué)的基本概念，最忌諱的是死記硬背，考生最好采用理解式記憶法，GMAT數(shù)學(xué)基本概念就能輕松搞定。