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Mean vs Median Information Note

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Why median is often more appropriate than mean

The CSO has produced a video which illustrates the difference between mean and median using house price as an example.

 

 

In statistics there are various measures that allow us to represent the characteristics of a group. The characteristics of interest could be, for example, the ages of a group of people, the wages of a group of workers or the price of a group of houses.

One of the most commonly used statistical measures is the mean (the ‘arithmetic mean’ to be precise, but more often simply termed the ‘average’). The mean is the sum of the characteristics of the group (e.g. ages, wages or prices) divided by the number in the group.

However, when we wish to describe the central tendency of the group, the mean is not the most appropriate measure.  For example, if the group contains some elements with exceptionally high characteristic values, these will push the arithmetic mean well above the central tendency of the group.

To represent the central tendency of a group, median is the appropriate statistical measure. The median is found by ordering the group characteristics in ascending value and selecting the middle one.

The median is a better measure of the central tendency of the group as It it is not skewed by exceptionally high or low characteristic values.

 

  • Gregg Patrick   (+353) 21 453 5202

  • Dan Gallagher   (+353) 21 453 5210

  • Email: rppi@cso.ie