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How do you work out the mean from the median?

Published in Statistics Fundamentals 2 mins read

Unfortunately, you cannot directly calculate the mean from the median without additional information about the dataset. The mean and median are different measures of central tendency, and knowing the median alone doesn't provide enough information to determine the sum of all observations, which is needed to calculate the mean.

The reference provides the following information:

  • Mean = Sum of all observations/Number of observations

This formula shows that to calculate the mean, you need both the sum of all the values in the dataset and the total number of values. The median, on the other hand, only tells you about the middle value (or values) when the data is ordered.

Why the Median Isn't Enough

The median only reflects the central point of the data. It doesn't tell you anything about the distribution of the other values.

Example:

Consider these two datasets:

  • Dataset 1: 2, 4, 6, 8, 10
  • Dataset 2: 2, 4, 6, 8, 100

In both datasets, the median is 6. However:

  • Dataset 1: Mean = (2+4+6+8+10) / 5 = 6
  • Dataset 2: Mean = (2+4+6+8+100) / 5 = 24

As you can see, even with the same median, the means are vastly different because of the different distributions of values.

In summary: You generally cannot determine the mean from the median without more information about the dataset's distribution. You need the sum of all the data points and the number of data points to calculate the mean.

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