# Introduction to Statistics

## Mean, Median, and Mode

Mean The mean is a number that shows the center of the data. Another word for mean is average and it is mathematically symbolized as x̄ (x-bar). However, when calculating the mean of the whole population, you use the Greek letter μ (mu) instead. To calculate the average of a sample, you sum all the observations,…

## Variance and Standard Deviation

The standard deviation (SD) is a measure of the spread of the data (how far from the normal it is). A number such as the mean or the standard deviation may be found either for an entire population (symbolized as σ or σx) or for a sample (symbolized as s) drawn from that…

## Statistics Definitions and Terminology

In statistics, an entire group of people or things is called a population or universe. A population can be infinite or finite. Examples of finite populations include the number of airplanes owned by an airline, or the potential consumers in a target market. Examples of infinite populations include the number of…