Clinical Biostatistics: Geometric mean length of hospital stay exercise, suggested answer 2

2. What is a geometric mean and how was it calculated?

Suggested answer

The geometric mean is found by multiplying all the n observations together and then taking the nth. root. For example, the geometric mean of 4 and 9 is 6, found by multiplying 4 by 9 to give 36 and taking the square (or second) root.

The geometric mean is usually smaller than the arithmetic mean. For 4 and 9 this is (4 + 9)/2 = 6.5.

In practice, we calculate it using a logarithmic transformation of the data. If we find the mean on the log scale, taking the antilog of this mean gives us the geometric mean.

Back to question.

Back to Clinical Biostatistics index.

To Martin Bland's home page.

This page maintained by Martin Bland.
Last updated: 31 July, 2006.

Back to top.