調和平均

The harmonic mean is calculated in three steps: first, take the reciprocal of each data value; second, calculate the arithmetic mean of these reciprocals; third, take the reciprocal of that result. This method avoids bias toward larger values present in simple arithmetic mean calculations, making it ideal for averaging rates and ratios.

When a vehicle travels the same distance at different speeds, the arithmetic mean is skewed toward larger values, giving an inaccurate average speed. The harmonic mean corrects this bias by weighting smaller values more heavily, providing the true average speed based on total distance divided by total time.

For a dataset with distinct positive values, the harmonic mean is always smaller than the geometric mean, which is always smaller than the arithmetic mean. This mathematical inequality demonstrates that the harmonic mean provides the most conservative average, making it useful for rate-based data.

The harmonic mean should not be used if any data value is zero, because calculating the reciprocal of zero is undefined and results in a mathematical error. Always verify that all values in your dataset are positive before applying the harmonic mean calculation.

In business, the harmonic mean is used to calculate metrics like the price-to-earnings ratio of a company. It effectively averages financial ratios and rates where smaller values should carry more weight, providing more accurate business performance indicators than the arithmetic mean.

The harmonic mean is one of three classical Pythagorean means alongside arithmetic and geometric means, all representing different approaches to central tendency. These measures of central tendency have been studied since ancient times and provide different representative values depending on data characteristics and distribution patterns.