Measures of Relative Position

Percentiles

A measure that calculates a value's relative position by dividing data into equal parts and determining the percentage of their location.

Quartiles

Values that divide the data into four equal parts after arranging it in order.

Q1

The first quartile, representing the value below which 25% of the data falls.

Q2

The second quartile, also known as the median, where 50% of the data falls below.

Q3

The third quartile, representing the value below which 75% of the data falls.

Box plots

Graphical representations of data that show the relative sizes of each quartile.

IQR (Interquartile Range)

The range or difference between the first and third quartiles, representing the middle 50% of the data.

Standard score (z-score)

A numerical measurement that describes a value's distance from the mean in terms of standard deviations.

Standard deviation

A measure of how spread out the values in a data set are from the mean.

Mean

The average of a set of numbers, calculated by dividing the sum of the values by the number of values.

Observation

A single data point that is measured within a statistical context.