mean

Arithmetic Mean (Average)

The sum of all values in a dataset divided by the count — the most common measure of central tendency.

When you'd see it: Any data team report. Revenue per customer, average order value, mean session duration — most summary numbers in business are arithmetic means. Also in model evaluation (mean error, mean squared error) and statistical tests.

Why it matters: The mean is useful when data is roughly symmetric, but it's sensitive to outliers. A dataset where 90% earn $50K and 10% earn $500K will have a mean well above $100K — a number that doesn't describe most people. Always ask whether the mean accurately represents the typical case, or whether median would be more honest.

Common mistakes: Using the mean when data is right-skewed (revenue, deal size, time-to-close) without checking the median. The mean will consistently overstate what a typical observation looks like in skewed distributions.

Related median, standard deviation, variance, outlier, descriptive statistics