3.13: 偏度的类型

Types of Skewness
JoVE Core
Statistics
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JoVE Core Statistics
Types of Skewness

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01:09 min
April 30, 2023

Overview

If the frequency distribution of a data set is more inclined towards smaller or larger values, the distribution is said to be skewed. If data values are skewed to the right, then the distribution is called positively skewed. Conversely, if the plot is skewed to the left, the distribution is called negatively skewed.

For instance, in the middle of a pandemic, the geographical distribution of vaccine coverage may be positively skewed towards populations in the global north countries. However, within any one such country, the vaccine distribution may be negatively skewed towards the percentage of the population, indicating that a significant fraction of the country’s population is vaccinated.

In the case of a skewed distribution, the mean and median also lie more decidedly towards the direction of the skew. However, by definition, the mode peaks at the distribution’s peak.

Transcript

回想一下,在数据集的分布中,如果图形的左半部分不是右半部分的镜像,则称数据是偏态的。

偏度有三种类型。如果图形延伸到左侧,在左侧形成较长的尾部,则称为负偏斜。如果图形延伸到右侧,在右侧形成较长的尾巴,则称其为正偏态。最后,具有对称或正态分布的图形的偏度为零。

表示负偏态数据的图形通常将平均值和中位数放在众数的左侧。

相反,正偏态数据集的平均值和中位数位于众数的右侧。

例如,年收入在一个城市居民(大量低收入人群)之间的分布表明正偏度。然而,学生在 Easy 考试中的分数分布,分数较低的学生较少,显示出负偏态数据。

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