如果将大量数据画成光滑的次数分布曲线，则可以认为：
  *算术平均数是数据分布的重心或平衡点
  *中数正好把分布分成相等的两半
  *分布的最高点对应众数

If a large amount of data is plotted as a smooth frequency distribution curve, it can be considered that:
  *The arithmetic mean is the center of gravity or equilibrium point of a data distribution.
  *The median exactly divides the distribution into two equal halves.
  *The highest point of the distribution corresponds to the mode.

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正偏态分布中，算术平均数＞中数＞众数；负偏态分布中，算术平均数＜中数＜众数；分布对称时，三个值重合。

In a normally skewed distribution, arithmetic mean>median>mode; In a negatively skewed distribution, the arithmetic mean<median<mode; When the distribution is symmetrical, the three values equal.

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