GRUBBSTEST function detects an outlier in a GTS (or a LIST of GTS), by applying a
This test is done under the assumption that the GTS follows an approximately normal distribution.
It tests whether there is exactly a single outlier in a GTS or not. For an iterative version which can detect multiple outliers, use instead
This function only applies to GTS of type DOUBLE.
Grubbs, Frank (February 1969). “Procedures for Detecting Outlying Observations in Samples”. Technometrics (Technometrics, Vol. 11, No. 1).