A non-parametric test for trend. Requires a single column of data. Missing values are deleted, and n adjusted accordingly. The procedure follows Gilbert (1987). Data x1, ... xn are assumed to be ordered in sequence of collection time, or in spatial sequence.
The test statistic S will be negative for a negative trend, zero for no trend, and positive for an increasing trend.
For n<=10, the p value is taken from a table of exact values (Gilbert 1987). For n>10, a normal approximation is used.
For mathematical details, see the Past manual.
Reference
Gilbert, R.O. 1987. Statistical methods for environmental pollution monitoring. Van Nostrand Reinhold, New York.