Spearman's Test for Trend
Spearman's Test for Trend
Description:
Spearman's Trend Test is provided in the USEPA Draft Unified Guidance (2004). The test is non-parametric, and therefore normality is not required for use.
Use:
As a non-parametric test to detect trends in data. In ChemStat's implementation, the test can be used to test for upward or downward trends, but not for two-tailed trends. The test can be performed at confidence levels up to 99.99%. To specify the confidence level, select Trend Analysis Options from the right-click menu over the report.
Remarks:
ChemStat uses the above formulas for all implementation of Spearman's trend test regardless of the number of samples or the number of ties. The Unified Guidance specifies slight difference formulas for the presence of ties, and for sample sizes less than 11, however the descriptions of those methods are insufficient to recreate the procedure in ChemStat.