Statistics symbols reference
A quick reference for the symbols used in statistics, with their meanings. A handy convention runs through them: Greek letters describe whole populations, while Latin letters describe samples.
Common statistics symbols
| Symbol | Meaning |
|---|---|
| μ (mu) | population mean |
| x-bar | sample mean |
| σ (sigma) | population standard deviation |
| s | sample standard deviation |
| σ² | population variance |
| s² | sample variance |
| N | population size |
| n | sample size |
| Σ (capital sigma) | summation, the sum of |
| P(A) | probability of event A |
| z | z-score, a standardized value |
| r | sample correlation coefficient |
| ρ (rho) | population correlation |
| p | population proportion |
| p-hat | sample proportion |
Greek versus Latin letters
A useful convention runs through statistics: Greek letters usually denote population parameters, the true but unknown values, while Latin letters denote sample statistics, the estimates computed from data. So mu and sigma describe the whole population, while x-bar and s describe a sample. Spotting which alphabet a symbol comes from tells you whether it refers to the population or a sample.
- Greek letters (mu, sigma, rho) usually mean population parameters.
- Latin letters (x-bar, s, r) usually mean sample statistics.
- μ is the population mean; x-bar is the sample mean.
- σ is the population standard deviation; s is the sample version.
- Capital sigma (Σ) means sum.
Related guides
See the Standard Deviation Guide and Statistics for Beginners.
FAQ
What does mu mean in statistics?
The Greek letter μ stands for the population mean, the average of an entire population.
What is the difference between sigma and s?
σ (sigma) is the population standard deviation; s is the sample standard deviation estimated from data.
Why does statistics use Greek and Latin letters?
Greek letters denote true population parameters; Latin letters denote sample statistics that estimate them.