Trimmed mean

A trimmed mean is the average of a data set computed after discarding a fixed percentage of the smallest and largest observations, making it more resistant to outliers.

ByHoang TruongUpdated July 11, 2026

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Ten sorted monthly commission payouts run €500 to €900, the last an unusually large one-off. The ordinary mean of all 10 is €6,120 ÷ 10 = €612. A 10% trimmed mean removes one value from each end, €500 and €900, leaving €520 through €660: €4,720 ÷ 8 = €590. Trimming removes the outlier's pull while keeping more information than the median alone.

Where it fits

TopicDescriptive StatisticsAdvancedSubjectData Analysis & StatisticsAdvanced

The formula

LaTeX

\bar{x}_{\text{trim}} = \frac{\sum x_{\text{remaining}}}{n - 2g}

Variables

$\overset{x}{ˉ}_{trim}$: Trimmed mean
$n$: Original number of observations
$g$: Number of observations trimmed from each end

Averages the data after discarding an equal number of the smallest and largest observations from each end.