concept

average

A statistical measure of central tendency, often the sum of values divided by the count.
12 related articles · 1 formulas

Description

The average, or arithmetic mean, is a measure of central tendency that summarizes a set of numbers by a single representative value. It is calculated by summing all values and dividing by the count. While simple, it is one of the most widely used statistical tools because it provides a quick sense of the 'typical' value in a dataset. However, it is sensitive to extreme values, which can skew the result away from the center of the bulk of the data.

History

The concept of the arithmetic mean dates back to ancient times; it was used by Babylonian and Greek astronomers to combine multiple measurements. The formal term 'average' entered English from Arabic maritime law, where it referred to a tax or loss-sharing arrangement.

How it works

To compute the average, you add up all the observations and then divide by the number of observations. For example, the average of 2, 4, and 6 is (2+4+6)/3 = 4. This operation gives equal weight to every data point, which is both its strength and its weakness: it uses all information but can be distorted by outliers. In scientific analysis, the average is often used alongside other statistics like the median or standard deviation to provide a fuller picture.

In practice

Used everywhere from calculating climate temperature trends to determining the average lifespan of a particle in physics experiments, and in everyday contexts like grade point averages.

Fun fact

In a famous example, the average number of legs per human is slightly less than two, because a small number of people have one leg or none—showing how averages can be misleading for skewed populations.

Concept graph →

Formulas

$$a(n) = \frac{1}{n!} \sum_{\pi \in S_n} \mathrm{fix}(\pi)$$
The number of unlabeled objects equals the average fixed points over permutations.
What is in the formula
a(n)variableNumber of unlabeled objects — count
nvariableSize parameter (e.g., number of elements) — count
πvariablePermutation in symmetric group — permutation
fix(π)variableNumber of fixed points of permutation π — count
∑operatorSum over all permutations — summation
1/n!operatorAverage over the group — average

Related articles · 12

Weather vs. Climate: How to Tell Noise from Signal
In winter, one part of town gets three times as much snow as the neighborhood next door. One year is a scorcher, the next is a cold snap. That's the whims of weather. But over decades, a different, slow shift emerges: winters, on average, get milder. Telling the two apart is the central challenge for climate scientists.
math.NT2026-08-012 minarXiv:2608.00615express
Numbers Hide Patterns
In 1998, mathematician David Boyd noticed something strange. He was studying the Mahler measure of polynomials, a quantity that gauges the "complexity" of their roots, and found that for a family of curves, it always equals a special rational number times the derivative of an L-function.
Signal Processing2026-07-161 minarXiv:2607.14738express
The Complexity of Crowds: Why Averages Fail
Usually, the complexity of systems, from satellite motions to heart rhythms, is assessed with averaged entropy (a measure of unpredictability, as understood by Boltzmann). But that's like evaluating the ocean only by wave height: the average figure hides the full richness of underwater currents.
cs.LO2026-07-151 minarXiv:2607.13531express
Chemical Soup Computes Numbers: How Reactions Became a Computer
In boiling soup, molecules collide chaotically and react. But if you measure how their concentrations change, patterns emerge. This is how carbon chemical networks work — mixtures of molecules that spontaneously 'cook' information, turning each reaction into an elementary computation. Previously they were used only for modeling nature.
eess.SY2026-07-151 minarXiv:2607.13914express
Epidemic Under Control: A Recipe for Systemic Approach
When a pipe bursts in the basement, a plumber acts step by step: locates the leak, measures the pressure, determines the cause, patches it up, and checks if it's dry. The same recipe — the standard model DMAIC — is being proposed against epidemics. First, they determine the scope — how many hospital beds are occupied, which industries are sagging.
Computer Vision2026-07-141 minarXiv:2607.12874express
Synthetic Deception: How Fake Images Teach Computers to See the Truth
A cook who learns to cook from hand-drawn pictures risks ruining every dish. The same trap awaits computer vision: models need thousands of labeled images, but collecting them manually is expensive and tedious. Synthetic frames solve the problem, but only if they look real.
q-bio.QM2026-06-151 minarXiv:2606.16726express
How Many Mice Does It Take to Understand the Microbiome?
When you're planning a renovation, you don't buy paint by eye: you measure the wall area. In science, deciding how many samples to collect is a similar guess, but the stakes are higher. Skimp on samples, and your study becomes a lottery: you might miss a real effect, or you might mistake noise for a discovery. Overshoot, and you're wasting tubes, months, and, in animal experiments, lives.
Statistical Mech2026-04-081 minarXiv:2604.07476express
Rhythm as a Dance of Order and Chaos
Music relies on repetition: we expect the beat to return, like a chorus coming back. But if you repeat the same thing for too long, it gets boring. The composer seems to walk a tightrope between the familiar and the unexpected. Scientists translated this balance into the language of physics.
Materials2026-03-201 minarXiv:2603.19905express
Heat Reveals the Strength of Aluminum
A piece of aluminum alloy is heated, and it quietly tells you about its strength. You just need to listen to that story in how the metal absorbs heat. The usual way to find out how strong an alloy is — pull it until it breaks. That takes time and destroys the sample.
Medical Physics2026-03-011 minarXiv:2603.01130express
Radiation Therapy with a Forecast: Predicting the Dose
During a course of radiation therapy, the tumor and surrounding tissues can shift or change size. Doctors regularly take images and sometimes adjust the plan to keep the radiation on target. But how do you know how much dose has already been delivered and how much is still to come? Usually, this is estimated using simple rules that don't account for uncertainty.
How the Brain Passes Thoughts
Imagine an office where employees exchange notes. When there are few tasks, everyone works independently. But when an urgent order arrives, some departments start actively messaging others, and the overall work becomes more coordinated. That's roughly how the brain behaves when we try to hold several things in mind at once.
How to Predict Heat a Year in Advance
On April 16, 2012, Washington experienced heat no one expected. The thermometer climbed 18 degrees above normal. Sixty days earlier, Bucharest and Kyiv had weather unusual for them. The link between these events was found by an algorithm that scans pairs of cities worldwide, looking for recurring coincidences.