STATS_WSR_TEST

Syntax

Description of the illustration stats_wsr_test.gif

Purpose

STATS_WSR_TEST is a Wilcoxon Signed Ranks test of paired samples to determine whether the median of the differences between the samples is significantly different from zero. The absolute values of the differences are ordered and assigned ranks. Then the null hypothesis states that the sum of the ranks of the positive differences is equal to the sum of the ranks of the negative differences.

This function takes three arguments: expr1 and expr2 are the two samples being analyzed, and the third argument is a return value of type VARCHAR2. If you omit the third argument, the default is TWO_SIDED_SIG. The meaning of the return values is shown in Table 5-10.

Table 5-10 STATS_WSR_TEST_* Return Values

Return Value	Meaning
`STATISTIC`	The observed value of Z
`ONE_SIDED_SIG`	One-tailed significance of Z
`TWO_SIDED_SIG`	Two-tailed significance of Z

One-sided significance is always with respect to the upper tail. The high value—that is, the value whose rejection region is the upper tail—is expr1.