Calculate the harmonic mean - the right average to use for rates like speed over equal distances.
The harmonic mean is the appropriate average for rates - most famously average speed when traveling equal distances at different speeds, where a simple average would overstate the true result.
Harmonic Mean = n ÷ Σ(1/xᵢ), where n is the count of numbers.
Traveling equal distances at 60, 40, and 80 mph gives a harmonic mean (true average speed) of about 56.47 mph - noticeably lower than the arithmetic mean of 60 mph.
Harmonic mean = n ÷ (sum of the reciprocals of each value), where n is the count of values.
It's preferred when averaging rates or ratios, like speeds over equal distances, since it correctly weights the different times each rate applies to.
Averaging speeds for a round trip covering the same distance at different speeds (e.g. 60 mph one way, 40 mph the other) — the true average speed is the harmonic mean, not the simple average.