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Nonparametric Tests 63<br />
KruskalWallisH (data(,), pairsig, h, p, diff(,))<br />
KruskalWallisH gives <strong>the</strong> Kruskal-Wallis H-test for independent samples. Pass a<br />
data(,) array that contains “treatments” in its columns; that is, each column is a<br />
dataset. Short columns can be padded out with missing values. Also pass pairsig, <strong>the</strong><br />
significance level at which columns are considered to be different. The test returns:<br />
h<br />
p<br />
diff(,)<br />
<strong>the</strong> H-hat statistic from <strong>the</strong> Kruskal-Wallis test; note that if more<br />
than 25% of all values are involved in ties, h is <strong>the</strong> corrected H-hat<br />
statistic<br />
significance probability of h (see Warning)<br />
pairs (i,j) of rank indices that test significantly different<br />
For example, you could pass pairsig = .05 to find all columns that are different at <strong>the</strong><br />
5% level. If <strong>the</strong>re are no such columns, Size(diff,1) is zero. But if <strong>the</strong>re are, say, three<br />
such pairs of columns i-j, i-k, and k-l, <strong>the</strong>n Size(diff,1) is 3; and diff(1,1) is i, diff(1,2) is<br />
j; diff(2,1) is i; diff(2,2) is k, etc.<br />
By default, pairwise significances are computed by via chi-square distributions, as<br />
given in Applied Statistics, p. 305. To switch to Dunn’s procedure for pairwise comparisons<br />
via normal distributions, call SetHtest(1) before calling this routine.<br />
———————————————————————————————————————<br />
x WARNING: For small samples, Size(data,1) < 5 or Size(data,2) < 4, p<br />
may be incorrect. Use a critical value table instead.<br />
———————————————————————————————————————<br />
See Applied Statistics, pp. 303-306, for a critical value table.<br />
Exception:<br />
755 Too many identical values for Kruskal-Wallis H test.<br />
See KRUSKAL, on your diskette, for an example.<br />
Friedman (d(,), cr(), fs, p)<br />
Friedman gives <strong>the</strong> Friedman rank-ANOVA test, a distribution-free two-way ANOVA<br />
for correlated samples.<br />
Input <strong>the</strong> data in d(,) where each column is a treatment. The output is:<br />
cr() column rank sums<br />
fs Friedman statistic<br />
p significance probability of fs (see Warning)<br />
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