The median is a common measure of the "centre" of a given dataset.
Definition
The median is a statistical measure that identifies the middle value of a dataset, effectively splitting it into two equal parts. In one half, all values are lower than the median, and in the other half, all values are higher.
For datasets with an even number of values, the median is determined by calculating the average (or mean) of the two middlemost numbers.
Properties of the Median
The median and mean both aim to provide a sense of the “centre” of a dataset. However, they are not the same and can have very different values.
- Outliers: Unlike the mean, which can be heavily influenced by outliers (extremely high or low values within the dataset), the median remains relatively unaffected. This makes the median a more "robust" measure in many scenarios.
- Symmetry vs. Skewness: In datasets that are symmetrically distributed, the mean and median tend to be close to each other. However, in skewed distributions, where data tails off to one side, the mean can be dragged toward the tail, while the median tends to stay more centrally located.
You can check your understanding of this lesson in the following quiz:
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Quiz: Estimating the Median (and Mean)
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