User Guide

498
Chapter 34
same number of observations, W is the rank sum of the group named first in the
Two-Independent-Samples Define Groups dialog box.
The Kolmogor
ov-Smirnov Z test and the Wald-Wolfowitz runs test are more
general tests that detect differences in both the locations and the shapes of the
distributions. The Kolmogorov-Smirnov test is based on the maximum absolute
difference
between the observed cumulative distribution functions for both samples.
When this difference is significantly large, the two distributions are considered
different. The Wald-Wolfowitz runs test combines and ranks the observations from
both group
s. If the two samples are from the same population, the two groups should
be randomly scattered throughout the ranking.
The Moses extreme reactions test assumes that the experimental variable will
affect som
e subjects in one direction and other subjects in the opposite direction. It
tests for extreme responses compared to a control group. This test focuses on the span
of the control group and is a measure of how much extreme values in the experimental
group inf
luence the span when combined with the control group. The control group is
defined by the group 1 value in the Two-Independent-Samples Define Groups dialog
box. Observations from both groups are combined and ranked. The span of the control
group is
computed as the difference between the ranks of the largest and smallest
values in the control group plus 1. Because chance outliers can easily distort the range
of the span, 5% of the control cases are trimmed automatically from each end.
Two-Independent-Samples Tests Define Groups
Figure
34-15
Two-In
dependent-Sampl es Define Groups dialog box
To split the file into two groups or samples, enter an integer value for Group 1 and
another for Group 2. Cases with other values are excluded from the analysis.