Mean
The average of all values in a dataset, calculated by summing all values and dividing by the count.
x̄ = (Σ x) / n
Median
The middle value when data are arranged in order. For even-sized datasets, it's the average of the two middle values.
Mode
The value(s) that occur most frequently in a dataset. A dataset may have one mode, multiple modes, or no mode.
Range
The difference between the maximum and minimum values in a dataset.
Range = max(x) - min(x)
Variance
A measure of data dispersion, calculated as the average of squared differences from the mean.
σ² = Σ(x - x̄)² / n
Standard Deviation
The square root of variance, representing the average distance from the mean.
σ = √σ²
Quartiles
Values that divide the data into quarters:
- Q1 (First quartile): 25th percentile
- Q2 (Second quartile): Median (50th percentile)
- Q3 (Third quartile): 75th percentile
IQR (Interquartile Range)
The range between the first and third quartiles, representing the middle 50% of data.
IQR = Q3 - Q1