Measures of Variability

Variability

The degree to which scores in a dataset differ from each other.

Measures of Central Tendency

Statistical measures used to describe the center of a dataset, commonly including mean, median, and mode.

Range

The difference between the largest and smallest scores in a distribution.

Deviation Score

The difference between an individual score and the mean of the dataset.

Sum of Squares

The total obtained from squaring each deviation score and summing them.

Variance

A measure of variability calculated by dividing the sum of squares by N minus one.

Degrees of Freedom (df)

The number of independent pieces of information available to estimate a parameter or a statistic.

Standard Deviation

A measure of how much scores in a dataset deviate from the mean on average.

Interquartile Range (IQR)

The difference between the upper (third) quartile and lower (first) quartile of a dataset.

Median

The middle value that divides a dataset into two equal halves.