Truncated mean

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A truncated mean or trimmed mean is a statistical measure of central tendency, much like the mean and median. It involves the calculation of the mean after discarding given parts of a probability distribution or sample at the high and low end, and typically discarding an equal amount of both.

For most statistical applications, 10 to 25 percent of the ends are discarded.

[edit] Advantages

The trimmed mean is a useful estimator because it is less sensitive to outliers than the mean but will still give a reasonable estimate of central tendency or mean for almost all statistical models. In this regard it is referred to as a robust estimator.

[edit] Drawbacks

The truncated mean uses more information from the distribution or sample than the median, so unless the underlying distribution is symmetric, the truncated mean of a sample is unlikely to produce an unbiased estimator for either the mean or the median.

[edit] Examples

The scoring method used in many sports that are evaluated by a panel of judges is a truncated mean: discard the lowest and the highest scores; calculate the mean value of the remaining scores.

The interquartile mean is another example when the lowest 25% and the highest 25% are discarded, and the mean of the remaining scores are calculated.