When the direction (and not the magnitude) of the difference within each matched paired in a paired experiment is known, the sign test can be used while the Wilcoxon Signed-Rank test cannot be used.

Sign Test

A nonparametric method utilized to identify if a median variance exists between paired data points.

Wilcoxon Signed-Rank Test

A nonparametric statistical hypothesis test used to compare two related samples, matched samples, or repeated measurements on a single sample to assess whether their population mean ranks differ.

Matched Paired

A study design in which subjects are paired based on certain criteria, with each pair receiving different treatments for comparison of the effects.