Mean, median, mode, range

Add all values, divide by count. Sensitive to outliers — one extreme value can skew it. Useful when you need a 'typical' value with all data weighed equally.

Middle value when data is sorted. If even count, average the two middle values. Resistant to outliers — that's why home prices report median, not mean.

Most frequent value. A data set can have multiple modes (or none if every value is unique). Useful for categorical data.

Max − min. The simplest measure of spread. Two data sets can have the same mean but very different ranges.