ranksum (Statistics Toolbox)

Wilcoxon rank sum test that two populations are identical.

Syntax

p = ranksum(x,y,alpha)
[p,h] = ranksum(x,y,alpha)

Description

p = ranksum(x,y,alpha) returns the significance probability that the populations generating two independent samples, x and y, are identical. x and y are vectors but can have different lengths; if they are unequal in length, x must be smaller than y. alpha is the desired level of significance and must be a scalar between zero and one.

[p,h] = ranksum(x,y,alpha) also returns the result of the hypothesis test, h. h is zero if the populations of x and y are not significantly different. h is one if the two populations are significantly different.

p is the probability of observing a result equally or more extreme than the one using the data (x and y) if the null hypothesis is true. If p is near zero, this casts doubt on this hypothesis.

Example

This example tests the hypothesis of equality of means for two samples generated with poissrnd.

x = poissrnd(5,10,1);
y = poissrnd(2,20,1);
[p,h] = ranksum(x,y,0.05)

p =

    0.0028

h =

     1