2.中數

　　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 /2 = 7. Note that the mean of these numbers is 7.5.

　　3.眾數：一組數中的眾數是指出現頻率最高的數。

　　例：the mode of 7，9，6，7，2，1 is 7。

　　4.值域：表明數的分布的量，其被定義為最大值減最小值的差。

　　例：the range of1，7，27，27，36 is 36-= 37。