The Friedman test is employed to compare two or more populations when the data are generated from a randomized block experiment,and are either ordinal or interval,but not normally distributed.

Randomized Block Experiment

An experimental design that groups participants into blocks based on certain characteristics before randomly assigning them to treatments, improving the experiment's accuracy by reducing variance.

Ordinal

Pertains to a categorical ranking where the order among values is significant but not the distance between them.

Interval

A range between two numbers or points, often used to specify the precision of an estimate or the coverage of a dataset.