Trimmed Mean Calculator Formula

Understand the math behind the trimmed mean calculator. Each variable explained with a worked example.

Use the Trimmed Mean Calculator

Formulas Used

Trimmed Mean (drop highest & lowest)

trimmed_mean = trimmed_sum / 3

Regular Mean

regular_mean = full_mean

Difference

difference = full_mean - trimmed_sum / 3

Variables

VariableDescriptionDefault
v1Smallest Value2
v2Value 210
v3Value 312
v4Value 414
v5Largest Value98
full_meanDerived value= (v1 + v2 + v3 + v4 + v5) / 5calculated
trimmed_sumDerived value= v2 + v3 + v4calculated

How It Works

How the Trimmed Mean Works

Approach

1. Sort the values from smallest to largest 2. Remove a fixed percentage from each end (here, one value from each end) 3. Average the remaining values

Trimmed Mean = Sum of remaining values / Count of remaining values

This technique protects the average from outliers while still using most of the data. A common choice is a 20% trimmed mean, which removes the top and bottom 20% of observations.

Worked Example

Data: 2, 10, 12, 14, 98. Compute the trimmed mean removing one value from each end.

v1 = 2v2 = 10v3 = 12v4 = 14v5 = 98
  1. 01Sorted values: 2, 10, 12, 14, 98
  2. 02Remove lowest (2) and highest (98)
  3. 03Remaining: 10, 12, 14
  4. 04Trimmed Mean = (10 + 12 + 14) / 3 = 12
  5. 05Compare: Regular Mean = 136 / 5 = 27.2 (heavily influenced by 98)

Ready to run the numbers?

Open Trimmed Mean Calculator